The best thing to do before any spell is cast is Learn about Wicca. Spell casting can be very dangerous without the proper knowledge of how to do it safely. There are several books and articles that will assist you in learning about Wicca.
Wicca isn't the only religion that has spell work in it. Read the thread titled "BTW Wicca vs Neo Wicca" that has been posted recently. Look at Paganism and the different paths that are there. Also before you cast any successful spell look at and work on the basics which are; grounding and centering meditation and circle casting.