1. a good quote is witty, clever, funny or inspirational;
2. a good quote is timeless; something you would read again and again.
3. a good quote is something strangers would post to facebook or tumblr, tweet on twitter, pin to pinterest or print out and hang on their walls.
4. a good quote is something you wouldn't be ashamed of if someone you knew read it.
5. a good quote follows the rules (i.e.: doesn't ask for faves or comments, etc)