I think advertising an affiliate site is similar to advertising a merchant site. General techniques: PPC, SEO, opt-in and so on. The difference is that apart from attracting visitors to the affiliate site itself, you'll have to advertise the product on it. Both advertisements should be relevant to attract sales not only clicks.
This all depends on what market the website is in. I do not advertise or market anywhere or send bulk emails out to just anyone. I have tried this and it just does not work (for me). I first look at who would be interested in what I had to offer and who would be interested in marketing your product. If I had a website that sold a dog training manual then I would search for dog related websites and offer the webmasters ??% on each sale that they made. Think about it!! The browsers that are viewing your affiliates website are there because they are interested in dogs so there is a far greater chance on them clicking your ad and making that all important sale. This creates a better affiliate and more sales.