Well... for one, call it RastafarI. No isms n' schisms
Rastafari is as much a social movement as it is a religion. Leaving out anything to do with marijuana, I think a lot of Rastafari has to do with socializing with, and being taken seriously by, other people who support this movement. Be sure you know the history and key figures (Marcus Garvey and Haile Selassie I, especially), and be sure you agree with the principles they teach.
Rastafari is not intellectual in the least. In fact, I'd say it's more about spiritual and political transformation via returning back to a state of nature ("naturality" is a word they kick around a lot).
There's a lot to be said for throwing off The System, and refusing to be a cog in the machine. But to truly do this (rather than just talk about it while smoking a lot of weed) entails some real sacrifices in today's world. I don't think one can live the American Dream, or a respectable middle class lifestyle in any developed nation, and be true to Rastafari's core principles. Like becoming a wandering ascetic, there is a good deal of voluntary marginalization involved. Don't let a bunch of romanticized reggae lyrics and heady nuggets fool you into underestimating how lonely a path this is likely to be, most of the time.
Rastafari carries the stigma of being Afrocentric, sometimes militantly so. This seems to be downplayed in recent years. Since Rastafari is a decentralized and loosely knit movement with no central spokesperson, I don't know quite what to make of this. I have a feeling many hardcore Rastas still have Afrocentric / Black Power leanings, but hold their tongues in order to protect their religion from being targets of anti-terrorism, or just from further marginalization. Certainly there are Rastas with no African heritage nowadays. But be aware that the religion still carries this stigma, and if you're clearly not African or a member of an indigenous people, you may have a hard time getting taken seriously, especially by non-Rastas.
Rastafari is built on a firm foundation of Evangelical Protestant Christianity and Ethiopian Orthodox (Coptic) Christianity. Some Rastas still consider themselves Christian at the same time. Some don't. It has borrowed superficial elements of Judaism and African folk religions, but beneath the surface, bears little similarity to either one. You'd do well to know the King James Version of the Old Testament / Hebrew Scriptures, if you want to get the references. The Book of Revelations and a non-Biblical Ethiopian book called the Kebera Negast would also help you in this regard. The rest of the New Testament seems to play little, if any, role in Rastafari.
Hope that helps. For the record, I'm a heavy marijuana smoker, partially for spiritual purposes, who likes a lot of Jamaican music and finds some of Rastafari's core principles noble and respectable. But I do not, and won't ever, consider myself Rastafari, because I don't live it and practice it.