How do you choose your sponsors?

[JenC]

Do you carefully inspect their program and research them? Do you just take referrals from friends? Or do you just pick them at random?

I am in the position to be looking for several new sponsors I haven't used before for a project I'm working on and I don't just want to pick them out of the blue. I would like to have some sort of method to my madness.

How do you choose which sponsors to promote?

NOTE: This is not a "spam me with" thread. I'm not looking for sponsor programs to come in and provide links, I am looking for unbiased opinions of how to choose the right sponsor. Also not looking for answers like "Blah Blah works good for me, try them".