A tip when searching would be to find who your competitors or sites similar to yours are linking to. Try typing link:
www.competitordomain.com into search engines and see what you find. You should be able to find many good potential affiliates that way.
Then after reviewing their site send them an insightful inquiry that shows them that you took the time to look at their site and also promotes conversation not necessarily selling them your stuff. I think this is the best way to recruit good affiliates, and that is what you should really want. It may be a little more time consuming but it is worth it. If they don't respond to the email after a while, try picking up the phone. Hope this helps, good luck!