All the above mentioned points plus:
• Don't "nice" someone else's throw until it has come to rest. It might have gone from "nice" to OB by that time.
Related: I also don't like it when I hit a long or low % putt for a bogey or worse and someone tells me it was a great putt. They might be trying to cheer me up but we're still competing and they prob just gained 2-3 strokes on me in 5 minutes too. When that happens, the irony makes me mental.
• Watch everyone else's throws, if possible. Then, when someone loses sight of their disc, the max # of people have a general idea where to look for it.
• Always help cardmates look for lost discs. It's sporting and makes the round proceed faster.
• Don't take longer than 30 seconds to throw.
• Buy a PDGA rulebook, read it and put it in your bag. They come with your PDGA membership or you can buy them online for <$5.
• No matter how badly you're playing, or how little fun you're having, always complete the tournament unless you're injured or some other emergency comes up. My dad taught me when I was young that playing sports requires you to enter an informal contract with your competitors. The contract is that everyone in the competition agrees to compete as hard as possible for the duration of the competition - that's it. The important point to consider is that when you're playing sports, you're not just there to win for yourself, you're there to provide competition to all the other players, even the players at the bottom of the table. It's funny but his lesson about not quitting a competition, that he taught me when I was playing little league, didn't come into focus until I began playing disc golf as an adult. I think it's because I mostly played team sports growing up and quitting was never really an option. But playing disc golf, on your own, without teammates or coaches, requires everyone to compete as hard as possible until the final throw. Otherwise, what's the point of it all?