Upvote for funny posts, posts that contribute to the discussion even if they drift a bit off topic, and anything that promotes positivity.
No upvotes/downvites for things I disagree with that are just differences in opinions, or something that is trying to be funny but doesn't work for me. Also posts I just don't understand or understand the context.
Downvotes for people being jerks, posting misinformation, promoting terrible stuff like fascism, racism, sexism, etc. It does mean I mostly downvote anything positive about US conservatives, but that is because they tend to promote those things I mentioned already.
I sometimes also downvote people who go overboard with generally positive things by assuming anything other than agreeing with their narrow view is automatically malicious. Some of us are trying and admitting we aren't perfect or that maybe there is more than one way to be supportive than the one they think the only way.