Hey bunni --
Start by reading the stickies on top - that should answer all of your basic questions. Then as more specific questions pop into your head, you can do a search. The most important thing is for you to educate yourself about the risks and rewards about them and then decide what you are comfortable w/ or not.
And the most important thing is to remember that no pill or injection will work unless you have your basic diet & training down and have already built a good base naturally. No quick fixes.
Good luck and READ READ READ!