Questions related to background checks

[LastVoter]

So I got an internship this summer that requires a background check, and I am not sure how to answer a few of them, and google didn't help. It asks me to list references and how I met them. What would be an acceptable answer for people that you have no professional relationship with? It also asks for immediate supervisors at your other jobs, and I have good reasons to think that he may not say the best things about me, how often do previous supervisors try to undermine your future job opportunities?

one more thing: I apologize for Bushie style attention whoring/flooding forum with boring sh**t in advance.