When I meet someone whom I consider a potential friend (as opposed to a passer-by), the very first thing I try to discern is if they are Republican. If they are, I move on. If they're Libertarian, I'm keeping my eye on them: chances are not good. Socialists are rare but acceptable. ; ) The next thing I try to find out is if they are Christian*. If they are, they had better be really subdued about it and open-minded to non-Christians, otherwise I'm already over them.
I should add: I don't do this by asking directly, but by looking for ancillary evidence.
Politics for me trumps religion… not sure why. Besides, most people on the right are also Xian, anyway.
Actually, I guess hygiene trumps both of them. I just don't like smelly people. Sorry, it's a personal failing of mine. So it goes.
I guess the next level of my radar would be geekdom. Do they recognize Firefly references? Do they appreciate my quote from Big Trouble In Little China?
If they pass those three (four, providing they don't stink) litmus tests, they've got a good shot of being a friend of mine. : )
(*Yes, specifically Christian. I haven't met anyone from another religion that bothered me. When I do, maybe I'll expand my list.)