My impression is that quotes only garner a lot of karma if they're heavy on the applause lights, though funny doesn't hurt. Finding new quotes which are likely to do well sounds rather difficult.

My impression is that those of my comments which go over 5 karma are very likely to be jokes, and at least at present, I have no ability to tell which jokes will go over that well. This doesn't seem worth trying to get stronger at, though perhaps the question is worth some thought.