Trolls are based on the "wild savages" you've seen in the movies or on TV, from King Kong to Discovery channel. If you've seen people hunting with spears, walking around in the forest without many clothes on, or dancing around in costumes and face paint in some kind of ritual you've never heard of, you've seen the apparent inspiration for trolls in World of Warcraft. The culture of Warcraft trolls are a mishmash of all the different myths and rumors that have grown up about some of the earth's indigenous peoples that live outside modern society: Strange voodoo beliefs and rituals? Check. Bloodthirsty headhunters with a taste for cannibalism? Check. Witch doctors, shrunken heads, human sacrifice, and rampant superstition? Check on all counts.
It's important to note here that troll culture is based on the myths about some indigenous people, not on their reality. Cannibalism, for instance, has been rare among human societies, nearly always viewed as anathema, but among the trolls of Azeroth, it appears to be the rule rather than the exception. Unbiased study of the world's primal religions has shown them to be far more sophisticated than early (and prejudiced) Western explorers ever imagined. Don't listen to the Jamaican accent trolls have in the game and assume that trolls are based on real life Jamaicans. There is nowhere near the correlation here that we might find with the dwarves and the Scots, or even the draenei and the eastern Europeans that they sound like. Indeed, one could argue that the choice of a Jamaican accent to represent the trolls and their culture reveals a great deal of ignorance we Americans have regarding Caribbean islanders -- but that's a discussion I'll not go into today.
Suffice it to say that as a member of the Darkspear tribe, the only tribe of trolls to join the Horde, your character living in a time of great change for your people. Your tribe is the first to embrace the more modern values promoted by Thrall, to take up the spiritual practices of shamanism, and to integrate itself with other races. Although the Darkspears have officially given up human sacrifice, cannibalism, and now tell you to "stay away from the voodoo," these practices are all elements of religion and superstition that your character would have grown up with, and may find it hard to let go of completely.