When you research on what affiliate programs to go for, always take into consideration the market you are targeting - as they are the ones who will make the conversion on your site. Also, always try to pick one that you you have knowledge on. Providing more than the product itself is a big plus - useful info (via a landing page), good advice and post sale customer support will give you more customers via referrals.
After that, it would also depend on how you market your product to the right market. This is also a factor to be greatly considered in determining your success. IMO, when you want to earn big, you should be ready to spend for it as well.
I always opt for PayPerClick to reach my target audience. Knowing how this system works would work to your advantage. Research (keywords), Selection (keywords and PPC provider), Implementation (bidding and start-up) and Analysis (which keywords worked best and cost vs. revenue).
What are your thoughts on selecting the right affiliate for you?