Affiliate marketing is basically getting a code from a company, pasting it into an advertisement and receiving money, when you make a sale. That’s the basics. The depth comes in when you try to use PPC and they won’t let you advertise your affiliate link. Keep in mind I only use PPC for split testing things, in the beginning. You can function with out a web site although it is better, when you have your own for tracking purposes.
The best advertising is free advertising. I suggest article marketing and forum marketing. It's a big ocean as one person has already replied. You'll need to research and make tests. Don't spend a lot of money because that’s not needed. You basically advertise your link one way or another.