If I may interject here...speacking as a wiccan -- or witch if you prefer -- I've been a member of the magickal community of nearly 14 years. Please, allow me to clear up a few things...
1. There is no such thing as white, or black, magick. The purpose behind the magickal working determines the path it will take.
2. Magick is not something to be played around with. If you're going to do it, then do it. Do not treat it as a hobby, and if you do begin to practice make sure that you're doing it for the right reasons and not because you're bored.
3. Real magick is nothing like you've seen on t.v. and in the movies. When you perform a magickal working, it may take time before you see any results. The universe will grant you what you seek when it thinks you should have it...but if it's for selfish reasons or if it may injure someone in one way or another, you will never see it come to pass.
4. Just because you can't see something, it doesn't mean it's not there.
5. To ask someone to prove themselves to you is neither fair nor right to either person. People expect their beliefs to be respected and in turn one should respect other peoples beliefs.
Now, it's not my intention to preach to anyone, I merely wanted to clear up a few misconceptions I read in this thread. Now that I've said my two cents, I'll sit back and let someone else have a go...