Some Principles of Action

1. Understand intelligence and its role in the world from a cosmological perspective. Because only when you understand it from a cosmological perspective will you be motivated to act, even when there are setbacks and things seem bleak. I would say this is the most important part. If you have trouble with philosophy, then embrace an appropriate religion, one that emphasizes compassion toward all sentient beings and in which there is a higher power who sides with the oppressed against the oppressors.
2. Support or build anything that furthers these values. This isn't "activism" in the ordinary sense of going to protests or getting pieces of paper signed. You can build the right kind of civilization in a lot of different ways. You should always support transparency and fairness in political processes, no matter what. For instance, support giving broad powers to IAEA inspectors in Iran, but more importantly, support giving those same powers to inspectors in the United States—not to punish the United States, but because if we do it, then that means everyone else will have to do it too.
3. Create and share knowledge in all its forms: literary, musical, scientific, philosophical, technological, visual, etc. Don't hoard knowledge; share it. Our ability to share knowledge is growing exponentially. It's a tremendous opportunity. Don't just share information. Think about it and relate it back to the broader picture: the story of our civilization and the essential conflicts in it. Oppose totalitarianism in all its forms. Always support individual rights.
4. Don't just go to protests. Protests are for old liberals stuck in the 60s and for anarchists hate technology and who juggle and do puppet shows. It's occasionally useful as a tactic, but mostly it's mouthwash for leftists, something to make them feel fresh.
5. Don't spend the majority of your time "critiquing" things. Of course one should be critical, i.e., use critical reasoning, in all things which are really worthwhile. But do it in the service of something constructive. Create knowledge and avenues of action with it. Don't use it to create despair or to make yourself feel powerless. Powerlessness is an illusion. Never in all of human history have individuals had more power to change the world.
6. Never martyr yourself or sacrifice yourself to a degree which is unreasonable. There is nothing noble in being oppressed or deprived. Remain aware of unfairness and privilege. Side with those who are treated unfairly against those who treat them that way. Always look for creative ways to use knowledge to subvert unfairness. But just because you're part of a privileged strata of society does not mean that all there is for you to do is to renounce your privilege and take up the cause of someone less privileged. People who come from a reasonably comfortable background and go to liberal arts colleges come away thinking (a) the world and everyone in it is screwed, (b) they're bad unless they're screwed too, and (c) the only thing you can do to redeem yourself is renounce privilege. This is the liberal arts school view of the world. It's pure preachy moralizing with no connection to reality. Ignore it.
   
   There's actually a lot you can do as a "privileged" person, and it doesn't require you taking the equivalent of friar's vows. (I really don't like the word "privileged"—try using that word with a lower-middle-class or working class family just because they happen to be white and see what kind of reaction you get. It's a bad strategy. It's a bad tactic.) Going to college gives you the ability to do knowledge-work. You can study part of the system as a whole—or even the system itself—and look for more avenues for action and intervention. There are a lot of things you can do once you move beyond self-flagellation.
7. There are so many avenues for positive action that there is no excuse for doing nothing. But I think the key to everything else is starting with the right perspective, the perspective of intelligence. If you believe we're living in a meaningless universe or that, as an individual with a modicum of awareness, you're like the last living survivor of a zombie apocalypse, you're going to have a really hard time doing anything besides laying in bed, drinking, or whining.
8. Sometimes less information is better than more. For example, if you read the news thoroughly every day, you're liable to form a skewed picture of what the world is like. The news of the day is always negative. You need to step back from that and take in, not necessarily more information, but a broader perspective. Creating knowledge sometimes requires us to destroy information or at least ignore it. That's how your mind recognizes things like faces or furniture—it destroys the background data and focuses on the pattern. That's what you need to allow your mind to do with our civilization and with some of human history.
9. The universe is intelligent, not dumb, i.e., it is part of its nature to give rise to more intelligent processes. Conscious moral awareness is therefore at home in the world. Making the world reflect our values is not a hopeless cause. It's the being of history itself. We're here for a reason—not one preordained by a higher power, whatever that means, but one given to us by ourselves for our own care and use.
10. That any of us exists at all is a mystery. That we exist now is very strange. We live in a time of unprecedented promise and peril. There probably has never existed a more important or interesting time to be alive. That's knowledge worth using.