Voodoo rituals, to my understanding, go like this:
You have Bondye almighty.
Under him you have the Loa. They're basically angels. They each have separate powers, personalities, and things they like.
What you have to do is get a Voodoo Priest, and get him to summon up a Loa into his body. This Priest is then called the Horse, because the Loa is essentially riding him in this world.
Then, you give the Loa an offering. I'll use Baron Samedi as an example. The Baron likes fine tobacco and quality rum. You let them finish this offering, then make your request. Information, something the Loa can do for you (the Baron, for example, can keep people alive) or to take your request to Bondye the creator.
Hey son, wanna' learn how ta' make witch balls?