You can start from here : http://paymentblogger.com/2007/03/26/an-introduction-to-affiliate-marketing/
consider to get any clickbank mall and promote all the clickbank products easily from a single link or promote the products of your choice using any keywords.
what stats are important when trying to find an e-book to sell? gravity? and when they say stuff like, "1 in 15" conversions is that accurate? or are they just saying that? last question, does anybody here have success with starting ppc campaigns and sending the user directly to the e-book page? I would think creating a landing page would be kind of pointless since the e-book page it self does all the selling, so don't think pre-selling would work. although if you had a complete website with all books that would be different.
If you don't understand (or can't afford PPC) then the easiest way to get started is to pick a product and build a blog around it. Example- One popular product is "burn the fat, and feed the muscle" (or something like that). Go get a free blog account at blogger or wordpress. Then all you have to do write posts related to that subject. When people read your blog they will also check out the product. You will slowly build content and begin to get traffic from search engines. Keep testing your layout and writing styles. If you put enough time into it then you will eventually make some sales. Take what you learned from your first blog and then build another for a different product. Sounds easy? It is...but you should also read posts about link building and article writing. Learn something new everyday and put some freakin effort into it. Eventually you will succeed. Disclaimer - if you don't like to write content then you will fail. Choose something you can write about that doesn't require you to do tons of research. (Don't write about making money online if you haven't made a cent.)
What you have to do is find programs on their network to promote on your site, in your blog or through PPC or landing pages. You have to do this by using their hoplinks.
Another suggestion is to pick a product you want to promote (something you're willing to do research on), and create a Squidoo lens around it. You need to address questions such as what kind of problems does the product solve for people who might be interested. You also need to research keywords people might use when looking for a product like the one you chose to sell. Yes, it can be a lot of work. But you can't expect to make money THAT easily now can you?