Not to sound smart, but the best thing you can possibly do for yourself is to buy a PhotoShop book. Nobody can tell you in a forum post how to do all of the things you will want to do with PhotoShop and you can learn very quickly by following along with examples. You'll be amazed what a powerful bit of software.
What Cindi said. And, if you've never done traditional hand painting before, it is a good idea to buy a book or two on that, so you will have ideas on what you would like to mimmick in Photoshop.
