The following document is in two parts: a fresh part created August 11, 2012, and an older part. There is overlap between them, but do not omit the second one, which had additional information.
Study the Bhagavad Gita, chapter 3, verses 8-25 (sacrifice and action without attachment); and chapter 4, verses 6-42 (the wisdom of the different kinds of sacrifice).
Observe the teaching about ritual and sacrifice; consider the personal and social pluses and minuses of these practices and the question about superstition. This is a stage in the evolution of religion, but not every ritual is primitive. For more details: http://www.hinduwebsite.com/hinduism/vedicsacrifice.asp
Observe that in the Bhagavad Gita the teaching about sacrifice turns into a generalized teaching about action (the primary meaning of karma).
The karma principle:
o Actions have consequences. We live in a universe of cause and effect.
o The wheel of action, impression, and desire: actions cause impressions in the doer; impressions cause desires to do the same thing again or to avoid doing the same thing again; and those desires cause future actions.
o What you do (for good or evil) comes back to you [on one level, immediately, on another level later on, and not always in this life]. “As you sow, so shall you reap”; “What goes around comes around.”
There should be no anxious compulsion (“attachment”) to succeed in action or fear of failure.
Dutiful action is performed with “the mind of perfect poise, housed in a body of clean habits, stabilized neural energies, and balanced chemical function.”
Dutiful, or ethical action, fulfills the duty (dharma) that comes with one’s stage in life and one’s position in society. Dutiful action is done for the good of society.
The highest action is done out of love for God. (By this teaching the Bhagavad Gita unites (i) karma yoga, the path (or discipline) of action, and (ii) bhakti yoga, the path of devotion [heartfelt devotion to a personal God].
Established in union [yoga], perform action [karma]" sings the Bhagavad-Gita (chapter 2, verse 48). How can we attain that goal? One way is called the path of karma yoga. The concept of karma is many-sided, and you will probably want to be selective in the meanings, if any, that you choose to put into practice. Do not worry about what is presently beyond your understanding. Work with what you do seem to understand, and do not worry about the rest. Ideally, you would begin by making your own study of the text on this topic. As an aid, here is one gleaning, with references to the translation and glossary by Barbara Stoler Miller.
Religion commonly provides moral and ethical guidance. The Bhagavad-Gita is one source for the Hindu ethics of performing your duty without attachment to the fruits of your action. For the Hindu tradition (for any tradition?) your station in life tells you many important things about your duties. You are a student? Then be a good student. You are a son or a daughter, brother or sister, a parent? Then fulfill these roles well. You are an employee, a citizen? Then do a good job and exercise intelligent patriotism. Of course there is more to say about dharma and about karma yoga, but these indications about the content of duty are enough for a beginning. The way to perform your duty is even more important. It is common to do the right thing because we fear the consequences of not doing so or because we are motivated by desire for the good consequences that we can expect will come back to us from the faithful performance of our duty. Desire for success and fear of failure drive many of our deeds. The karma principle affirms that the universe will respond to you, in this life and or the next. Your good deeds will not go unrewarded. Being aware of the ultimate reward, it takes a certain reorientation to act without being "attached" to these fruits of action. Study the Bhagavad-Gita as a whole for yourself to discover what it means to act without attachment to the fruits of action.
Karma means action. A person has to perform his or her duty, sacred duty (dharma). One is to act "because it must be done" (18.9). Performing duty sustains oneself, the society, and the cosmos (3.14,24,26). Have faith in sacred duty (9.3). You must attend to your own duty, not someone else's (3.35). In extreme cases, to perform duty may appear to harm other people, but everyone's true self (atman) is eternal and cannot be harmed (2.31). The self is beyond action, does not act (3.27). It is one's nature that acts (13.29). Act with the body only (4.21). Nevertheless, action is better than inaction (5.2; 6.1); indeed it is impossible not to act (3.5). The enlightened person sees inaction in action, action in inaction (4.18). Imitate God (incarnate as Krishna), who acts without needing to act (3.23). Action is the source of all (4.32). Action leads to maturity (6.3) and to liberation (moksha; 4.32).
Actions have consequences. The universe responds to you, sooner or later, according to the quality of your actions. Action (unenlightened) gives rise to impressions, which give rise to desire (and aversion), which cause action, a cycle involving rebirth, reincarnation (6.40-45). Miller writes that "karma is a store of good and bad actions, accumulated over many lives, and it is this store of actions that binds one to phenomenal existence" (glossary, 163).
What is the right basis for action? Without attraction to the fruits of action, one is to be established in discipline (yoga, union with supreme reality; 2.47-48), with one's mind on the eternal spirit self (atman; 3.30). One should delight in the Infinite Spirit (Brahman, the omnipresent, impersonal, ultimate reality; 3.15,17). Delighting in oneSelf, one does not act from a drive or need (3.23). It is in fact possible to attain realization of the Infinite Spirit by contemplating action (4.24).
Many virtues are manifest in right action: fearlessness, purity, determination in the discipline of knowledge, charity, sacrifice, study of sacred lore, penance, honesty, non-violence, truth, absence of anger, disengagement, peace, loyalty, compassion for creatures, lack of greed, gentleness, modesty, reliability, brilliance, patience, resolve, clarity, absence of envy and of pride (16.1-3). Be free of desire and anger, always content and independent (4.20), indifferent to success and failure, pleasure and pain. Be hostile to no creature (11.55). In general, do not be emotionally involved with your action, but be established beyond the level of [material] emotions.
What is the supreme, religious motivation for action? Being devoted to God in loving worship leads to the performance of one's sacred duty (9.30-31). God is the basis of eternal sacred duty (14.27). Imitate God (3.23). All actions should be surrendered to God (3.30). Leave the consequences to God (18.6). All actions should be done as a [religious] sacrifice (3.9). Act only for God (11.55).