[NOTE:  What follows is a decent summary of the basic approaches of the four classical types of yoga (bhakti, jnana, karma and raja).  It is just a summary, and presents the material from a modern point-of-view, rather than from a classical one.  Still, it will serve to introduce the various paths.  Clicking on the link above will take you to The Vedanta Society where you will find other on-line materials.  -- W. Weinstein]

Meaning of Yoga

While in recent years the word "yoga" has been heard more in gyms than in religious discourse, "yoga" in its original sense has little to do with exercise. "Yoga" comes from the Sanskrit verb "yuj," to yoke or unite. The goal of yoga is to unite oneself with God; the practice of yoga is the path we take to accomplish this.

Spiritual aspirants can be broadly classified into four psychological types: the predominantly emotional, the predominantly intellectual, the physically active, and the meditative. There are four primary yogas designated to "fit" each psychological type.

We should state from the beginning that these categories are not airtight compartments. Indeed, it would be psychologically disastrous for anyone to be completely emotional, completely intellectual, completely active or completely meditative. Each yoga blends into the next; each yoga balances and strengthens the others.
 

The Path of Love: Bhakti Yoga

For those more emotional than intellectual, bhakti yoga is recommended. Bhakti yoga is the path of devotion, the method of attaining God through love and the loving recollection of God. Most religions emphasize this spiritual path because it is the most natural. As with other yogas, the goal of the bhakta, the devotee of God, is to attain God-realization--oneness with the Divine. The bhakta attains this through the force of love, that most powerful and irresistible of emotions.

Love is accessible to everyone: we all love someone or something, frequently with great intensity. Love makes us forget ourselves, our whole attention being devoted to the object of our adoration. The ego loosens its grip as we think of our beloved's welfare more than our own. Love gives us concentration: even against our will, we constantly remember the object of our love. In an easy and totally painless way, love creates the preconditions necessary for a fruitful spiritual life.

Vedanta therefore says, Don't squander the power of love. Use this powerful force for God-realization. We must remember that when we love another we are really responding--though unconsciously--to the divinity within him or her. As we read in the Upanishads, "It is not for the sake of the husband that the husband is dear, but for the sake of the Self. It is not for the sake of the wife that the wife is dear, but for the sake of the Self." Our love for others becomes unselfish and motiveless when we are able to encounter divinity in them.

Unfortunately, we usually misplace our love. We project our vision of what's true, perfect, and beautiful and superimpose it upon whomever or whatever we love. It is God alone, however, who is True, Perfect, and Beautiful. Vedanta therefore says: Put the emphasis back where it belongs--on the divine Self within each person that we encounter. That is the real object of our love.

Rather than obsessing on a limited human being, we should think of God with a longing heart. Many spiritual teachers have recommended adopting a particular devotional attitude towards God: thinking of God as our Master or Father or Mother or Friend or Child or Beloved. The determining factor here is, Which attitude feels the most natural to me and which attitude brings me closest to God?

Jesus looked upon God as his Father in Heaven. Ramakrishna worshipped God as Mother. Many great saints have attained perfection through worshipping God as the baby Jesus or the baby Krishna. Many have attained perfection through worshipping Christ as the bridegroom or Krishna as the beloved. Others have attained perfection through worshipping God as their master or friend.

The point to remember is that God is our own, the nearest of the nearest and dearest of the dearest. The more our minds are absorbed in thoughts of Him--or Her as the case may be--the closer we shall be to attaining the goal of human life, God-realization.

Many people are drawn to worshipping God through love and devotion. Yet other spiritual aspirants are more motivated by reason than by love; for them, bhakti yoga is barking up the wrong spiritual tree. Those who are endowed with a powerful and discriminating intellect may be better suited for the path of jnana yoga, striving for perfection through the power of reason.
 

The Path of Knowledge: Jnana Yoga

Jnana yoga is the yoga of knowledge--not knowledge in the intellectual sense--but the knowledge of Brahman and Atman and the realization of their unity. Where the devotee of God follows the promptings of the heart, the jnani uses the powers of the mind to discriminate between the real and the unreal, the permanent and the transitory.

Jnanis, followers of nondualistic or advaita Vedanta, can also be called monists for they affirm the sole reality of Brahman. Of course, all followers of Vedanta are monists: all Vedantins affirm the sole reality of Brahman. The distinction here is in spiritual practice: while all Vedantins are philosophically monistic, in practice those who are devotees of God prefer to think of God as distinct from themselves in order to enjoy the sweetness of a relationship. Jnanis, by contrast, know that all duality is ignorance. There is no need to look outside ourselves for divinity: we ourselves already are divine.

What is it that prevents us from knowing our real nature and the nature of the world around us? The veil of maya. Jnana yoga is the process of directly rending that veil, tearing it through a two-pronged approach.

An Unreal Universe

The first part of the approach is negative, the process of neti, neti--not this, not this. Whatever is unreal--that is, impermanent, imperfect, subject to change--is rejected. The second part is positive: whatever is understood to be perfect, eternal, unchanging--is accepted as real in the highest sense.

Are we saying that the universe that we apprehend is unreal? Yes and no. In the absolute sense, it is unreal. The universe and our perception of it have only a conditional reality, not an ultimate one. Under certain conditions, a coiled rope may be mistaken for a snake. So, in a similar manner: the rope, i.e., Brahman, is perceived to be the snake, i.e., the universe as we perceive it. While we are seeing the snake as a snake, it has a conditional reality. Our hearts palpitate as we react to our perception. When we see the "snake" for what it is, we laugh at our delusion.

Similarly, whatever we take in through our senses, our minds, our intellects, is inherently restricted by the very nature of our bodies and minds. Brahman is infinite; it cannot be restricted. Therefore this universe of change--of space, time, and causation--cannot be the infinite, all-pervading Brahman. Our minds are circumscribed by every possible condition; whatever the mind and intellect apprehend cannot be the infinite fullness of Brahman. Brahman must be beyond what the normal mind can comprehend; as the Upanishads declare, Brahman is "beyond the reach of speech and mind."

Yet what we perceive can be no other than Brahman. Brahman is infinite, all-pervading, and eternal. There cannot be two infinites; what we see at all times can only be Brahman; any limitation is only our own misperception. Jnanis forcefully remove this misperception through the negative process of discrimination between the real and the unreal and through the positive approach of Self-affirmation.

Self-Affirmation

In Self-affirmation we continually affirm what is real about ourselves: we are not limited to a small physical body; we are not limited by our individual minds. We are Spirit. We were never born; we will never die. We are pure, perfect, eternal and free. That is the greatest truth of our being.

The philosophy behind Self-affirmation is simple: as you think, so you become. We have programmed ourselves for thousands of lifetimes to think of ourselves as limited, puny, weak, and helpless. What a horrible, dreadful lie this is and how incredibly self-destructive! It is the worst poison we can ingest. If we think of ourselves as weak, we shall act accordingly. If we think of ourselves as helpless sinners, we will, without a doubt, act accordingly. If we think of ourselves as Spirit--pure, perfect, free--we will also act accordingly.

As we have drummed the wrong thoughts into our minds again and again to create the wrong impressions, so we must reverse the process by drumming into our brains the right thoughts--thoughts of purity, thoughts of strength, thoughts of truth. As the Ashtavakra Samhita, a classic Advaita text, declares: "I am spotless, tranquil, pure consciousness, and beyond nature. All this time I have been duped by illusion."

Jnana yoga uses our considerable mental powers to end the duping process, to know that we are even now--and have always been--free, perfect, infinite, and immortal. Realizing that, we will also recognize in others the same divinity, the same purity and perfection. No longer confined to the painful limitations of "I" and "mine," we will see the one Brahman everywhere and in everything.
 

The Path of Work: Karma Yoga

Karma yoga is the yoga of action or work; specifically, karma yoga is the path of dedicated work: renouncing the results of our actions as a spiritual offering rather than hoarding the results for ourselves.

Karma is both action and the result of action. What we experience today is the result of our karma--both good and bad--created by our previous actions. This chain of cause and effect that we ourselves have created can be snapped by karma yoga: fighting fire with fire, we use the sword of karma yoga to stop the chain reaction of cause and effect. By disengaging the ego from the work process, by offering the results up to a higher power--whether a personal God or to the Self within--we stop the whole snowballing process.

Whether we realize it or not, all of us perform actions all the time since even sitting and thinking is action. Since action is inevitable, an integral part of being alive, we need to reorient it into a path to God-realization. As we read in the Bhagavad-Gita, one of Hinduism's most sacred scriptures:

All of us tend to work with expectations in mind: we work hard in our jobs to get respect and appreciation from our colleagues and promotions from the boss. We clean our yards and make them lovely with the hope that our neighbors will be appreciative if not downright envious. We work hard in school to get good grades, anticipating that this will bring us a fine future. We cook a splendid meal with the expectation that it will be received with plaudits and praise. We dress nicely in anticipation of someone's appreciation. So much of our lives is run simply in expectation of future results that we do it automatically, unconsciously.

This, however, is a perilous pattern. From a spiritual viewpoint, all these expectations and anticipations are Trojan horses that will bring us misery either sooner or later. Misery is inevitable because our expectations and desires are unending and unappeasable. We will live from disappointment to disappointment because our motivation is to gratify and enlarge the ego; instead of breaking the bonds of karma, we are forging fresh chains.

No matter whether we are devotional, intellectual or meditative by temperament, karma yoga can easily be practiced in tandem with the other spiritual paths. Even those who lead a predominantly meditative life benefit from karma yoga, for thoughts can produce bonds just as effectively as physical actions.

Just as devotees offer flowers and incense in their loving worship of God, so can actions and thoughts be offered as divine worship. Knowing that the Lord exists in the hearts of all creatures, devotees can and should worship God by serving all beings as his living manifestations. To paraphrase Jesus Christ: What we do for the least of our brothers and sisters, we do for the Lord himself. "A yogi," says the Bhagavad-Gita, "sees Me in all things, and all things within Me." The highest of all yogis, the Gita continues, is one "who burns with the bliss and suffers the sorrow of every creature" within his or her own heart.

Jnanis take a different but equally effective tack. They know that although the body or the mind performs action, in reality they do no work at all. In the midst of intense activity, they rest in the deep stillness of the Atman. Maintaining the attitude of a witness, jnanis continually remember that they are not the body, not the mind. They know the Atman is not subject to fatigue or anxiety or excitement; pure, perfect and free, the Atman has no struggle to engage in, no goal to attain.

The point of all the yogas is to spiritualize our entire life instead of compartmentalizing our days into "secular" and "spiritual" zones. Karma yoga is particularly effective at this since it won't allow us to use activity as an escape. By insisting that life itself can be holy, karma yoga gives us the tools of everyday life to cut our way to freedom. To quote again the Bhagavad Gita regarding karma yoga:

The Path of Meditation: Raja Yoga

Raja yoga, is the royal path of meditation. As a king maintains control over his kingdom, so can we maintain control over our own "kingdom"--the vast territory of the mind. In raja yoga we use our mental powers to realize the Atman through the process of psychological control.

The basic premise of raja yoga is that our perception of the divine Self is obscured by the disturbances of the mind. If the mind can be made still and pure, the Self will automatically, instantaneously, shine forth. Says the Bhagavad Gita:

If we can imagine a lake that is whipped by waves, fouled by pollution, muddied by tourists and made turbulent by speedboats, we'll get a fair assessment of the mind's usual state.

Should anyone doubt this assertion, let the intrepid soul try to sit quietly for a few minutes and meditate upon the Atman. What happens? A thousand different thoughts fly at us, all leading the mind outward. The fly buzzing around suddenly becomes very important. So does the thought of dinner. We now remember where we left the keys. The argument we had yesterday becomes even more vivid and powerful; so does the perfect retort that we've cleverly composed during our "meditation." The minute we stop thinking one thought, another jumps in with equal force. Were it not so dismaying, it would be funny.

Most of the time we remain unaware of the mind's erratic movements because we are habituated to giving our minds free reign: we've never seriously attempted to observe, let alone train the mind. Like parents whose indiscipline has created children that everyone dreads, our lack of mental discipline has created the turbulent, ill-behaved minds that have given us endless difficulty. Without psychological discipline, the mind becomes the mental equivalent of the house ape. And all of us, sadly enough, have suffered mental agony because of it.

Mastering the Mind

While we may have grown accustomed to living with an uncontrolled mind, we should never assume that it's an acceptable, if not inevitable, state of affairs. Vedanta says that we can master the mind and, through repeated practice, we can make the mind our servant rather than being its victim. The mind, when trained, is our truest friend; when left untrained and reckless, it's an enemy that won't leave the premises.

Now, instead of the polluted lake we previously envisioned, think of a beautiful, clear lake. No waves, no pollution, no tourists, no speedboats. It's clear as glass: calm, quiet, tranquil. Looking down through the pure water, you can clearly see the bottom of the lake. The bottom of the lake, metaphorically speaking, is the Atman residing deep within our hearts. When the mind is pure and calm, the Self is no longer hidden from view. And, Vedanta says, that mind can be yours. How? To again quote the Bhagavad Gita:

The mind is cleansed and made tranquil through the repeated practice of meditation and through the practice of moral virtues.

Popular wisdom aside, there is no way to practice meditation without practicing moral virtues in tandem. To try to do otherwise is as effective as sailing the ocean with a leaky boat.

For such a Herculean task as realizing the Atman, all areas of the mind must be fully engaged. We cannot compartmentalize our life and assume that we can have both a "secular" area (in which we can live as we please) and a "spiritual" area. Just as we can't cross the ocean in a leaky boat, so we can't cross the ocean with two legs in two different boats. We must fully integrate all aspects of life and direct our energies towards the one great goal.

This doesn't mean that in order to realize God a person must totally renounce the world and live in a cave, monastery or convent. What it does mean is that all aspects of our life must be spiritualized so that they can be directed towards attaining the goal of God-realization.

Because raja yoga is the path of meditation, it is--when practiced exclusively--generally followed by those who lead contemplative lives. Most of us will never fall into that category. Raja yoga is, however, an essential component of all other spiritual paths since meditation is involved in the loving recollection of God, mental discrimination, and is an essential balance to selfless action.

Meditation

As for directions on how to meditate and what to meditate upon, such issues must be taken up directly with a qualified spiritual teacher. Meditation is an intensely personal matter; only a genuine spiritual teacher can accurately gauge the student's personal tendencies and direct the student's mind accordingly.

Further, spirituality is caught, not taught. A genuine spiritual teacher ignites the flame of spirituality in the student by the power of his or her own attainment: the student's candle is lit by the teacher's flame. Our candles cannot be lit by books any more than they can be lit by unqualified teachers who speak religion without living it. True spirituality is transmitted: only pure, unselfish teachers who have achieved some level of spiritual awakening can enliven our own dormant flame.

That said, some basic guidelines can be given: any concept of God--whether formless or with form--that appeals to us is helpful and good. We can think of God as being present either outside of ourselves or inside. Ramakrishna, however, recommended meditating upon God within, saying "the heart is a splendid place for meditation." Repetition of any name of God that appeals to us is good, so is repeating the holy syllable "Om." It's helpful to have a regular time for meditation in order to create a habit; it's also helpful to have a regular place for meditation that is quiet, clean, and tranquil.