I upvote comments that contribute to the discussion, even if I disagree. I downvote comments that detract from the discussion or use slurs. Comments that add nothing but aren’t harmful I leave unvoted.
Posts are a little different. I upvote posts that are interesting (or sparked interesting comments) and on-topic for the muni. I downvote posts that are off-topic and videos posted without a text summary. Posts which don’t interest me but are on-topic I leave unvoted.