These are just my opinions. Some people might disagree. Fine with me.
When you want to give up then resign instead of abandoning the game.
Wait until it's your turn to move before resigning.
Do not resign too soon. Make your opponent earn it. He or she could make a mistake and you could get a draw or win it. Too many people are quitters.
If an opponent would rather be checkmated instead of resigning that's perfectly OK and it's wrong to complain about it. I look at it as an opportunity to practice winning as fast as possible.
It's wrong to ask for a draw if you're behind in material or you have an inferior position. You are only annoying your opponent who is trying to think.
I suggest it's often wrong to ask for a draw because it's distracting. I prefer to try to repeat the position 3 times. If my opponent doesn't cooperate then the answer is no.
If your opponent played brilliantly to win the game it's nice to write in the chat room "Well done".
I consider my opponent who I'm trying to kill to be my friend who shares my love for chess and this fantastic website.