Well, there's the cheap and easy way, or the advanced way. Judging by the thread title, you want advanced. Myself, I am not very knowledgeable in vectors, it hasn't interested me enough to learn
http://www.melissaclifton.com/tutorial-vector.html is the first result on google for me, seems like a pretty in depth tutorial.
I forgot to ask, are you using photoshop, or something else like gimp?