"Be civil. Don't say things you wouldn't say in a face to face conversation.
"When disagreeing, please reply to the argument instead of calling names. E.g. 'That is an idiotic thing to say; 1 + 1 is 2, not 3' can be shortened to '1 + 1 is 2, not 3.'"
Not to be an old-timer snob (because I haven't actually been here very long, but I hung onto reddit from the start until I couldn't take it any longer, and I really like the current style here)... anyway...
Here's an idea: Don't allow people to up-vote on ANYTHING (stories or comments) until they get a karma of 25.
I'd like people to take note of the not complaining about being downvoted item. Though it only applies to the discussion of downvoting in general by extension, I'd really rather not see another thread about the evils of the downvote button. If fear of karma loss stops you from voicing an unpopular opinion then I'd rather not hear from you.