To be the third or fourth echo here, there's a LOT of good advice here. That said, let me offer a little bit of what I've learned along the way that hasn't been brought up:
1. Don't think about your score. Once a hole is over, it's over. You can't go back and do it over....until the next round, anyway. If it was a great hole for you, don't get cocky and start throwing up dubious, miracle shots if you get in trouble thinking it's your lucky day. Play smart. Conversely, if you had a bad hole, don't let it shake your confidence and allow you to get desperate, throwing up dubious, miracle shots in order to make up for that bad hole. Again, play smart. Every hole is a complete reset: You can either come back strong or fall apart completely if you get too caught up in your score.
2. If you're the score-keeper, always ask your cardmates after every hole what they got, repeat it, and then write it down. It keeps people honest.
3. NEVER announce the scores out loud or tell someone how far up, how far back, or where they stand in relation to others. If someone wants to know where they stand, show them the scorecard and let them see for themselves. They'll know how they fared after the round is over. This will keep you from getting a lot of grief. Trust me....I learned this the hard way.
4. Don't "nice" people. It's a hard habit to break, especially if you play a lot. We all know that there's nothing you could say to anyone that would alter the trajectory of the disc once it's left the hand, but some players are SUPERstitious about this and it pisses them off. Avoid it altogether if possible. Or wait until the disc has come to a complete stop in a good spot to say something if you absolutely must acknowledge their shot.
5. Play YOUR game and have FUN!