Recomendations from private conversations with other webmasters I trust is my first consideration.
If I like the content so much I feel the urge to stop what I'm doing so I can pleasure myself the moment I first come across it... I'll probably sign up on the spot, but I may not promote.
Everything else goes into my "sponsors to consider" favorites folder, broken down by billing processor. CCBill sponsors get priority.
If I need a niche, fresh content, or sponsor links to stuff somewhere, or I'm not happy with past performers, I hunt through my favorites and make direct comparisons on those factors I've gained the experiene enough to estimate as reasons why I may or may not make money.
Also, every so often I'll sign up with a program on a whim and test it out just to feed the chaos element.
