Well .. You can join CJ, and they are approving 98% of their affiliates, so it's easy to start and easy to earn ( nothing big, but .. a few $ you will earn ) !
You can find what they are looking for in the Terms & Conditions when you sign up for CPA sites. Many sites will give you a brief rundown on their sign up page as well. I have several listed below if you have a particular question about any of them, let me know.
You can try Pepperjam. Their ads apparently convert 75% better than other affiliate ads. But getting in might be a bit hard. But it never hearts...
i have a ton in my link...if you have questions let me know. I'd be happy to help! IncentReward, MaxBounty, Affiliopolis, and Iron Offers a few of my faves.