When I learned to play many years ago, the basic rule was always say "Good Game" after the game, no matter how poorly you or your opponent played. Other than that, I'd say, resign when you are being beat handily, and especially if you are playing a clearly superior player. And do not offer a draw when you are well behind.
Chess manners

Don't gloat during or after a game, don't claim to have played better after losing "if only I hadn't done____" Winning or losing, I like to make my moves calmly, but some people bash out good moves or shake their head when they're losing. Body language isn't bad etiquette as long as it's not extreme.
Tournament chess add shaking hands before and after. Sometimes I say "thanks for the game" (win or loss) because I mean it, without an opponent I can't play.

Shake hands, sit down, play a game, shake hands, cry, go home.
Is it really good manners to cry before you go home? I'd think you should wait at least until you get into your car.

Shake hands, sit down, play a game, shake hands, cry, go home.
Is it really good manners to cry before you go home? I'd think you should wait at least until you get into your car.
After the game is over, all bets are off!

Shake hands, sit down, play a game, urinate on board, cry, go home, never play again.
DC-poop, that's not what I said.

I figure it's always safe to quote a chess legend when losing...such as:
"Gegen diesen Idioten muss ich verlieren!"

When playing against a woman, you should stand up whenever she stands - if you are a man, obviously.

"Just trying my best keeping the site of chess ladies and gentlemen. Is that to much to ask for? role model"
- Jose Capablanca

DC-poop, that's not what I said.
No kidding. It's one thing to change someone's words if it's made clear that it's a parody of what they really said, and that they didn't really write those words. Or to selectively quote, leaving out irrelevant portions of the original text. But to insert completely different words and still use the quoting formatting so that anyone who sees only your message thinks they're seeing the original words from the other person is just tacky, tacky, tacky. Regardless of the reason.

Shake hands, sit down, play a game, shake hands, cry, go home.
Is it really good manners to cry before you go home? I'd think you should wait at least until you get into your car.
This is great!

When playing against a woman, you should stand up whenever she stands - if you are a man, obviously.
Does this apply to my wife too?

Crosspinner wrote: Does this apply to my wife too?
Certainly - and bring her some flowers occasionally.

Maybe if they two posts are far apart, but when the OP and the parody are posts 3 and 7 it's not real difficult to realise the words have been changed, is it?
And what happens if 5 pages down the road someone quotes just your post? Now how close together are your made up words to the genuine ones?
Gee, I would think if you thought what you wrote was so hilarious (it wasn't) you'd have wanted to take credit for it yourself instead of making it look like someone else wrote it.
You're welcome for the reminder of proper quoting manners.

Always say "good luck" and "good game" while shaking hands (which of course cannot be done on the internet) and maybe the occasional "rematch?"

DC-poop, that's not what I said.
No kidding. I don't know what to say to that, exactly. But I hope that we can all use different words and quoting formatting so that anyone who sees only your message thinks they're seeing the original words from the other person.
I'm sorry cystem but I think that's just tacky!

Bullet pointed arguments ftl = "DC-poc wrote: Occasionaly I forget what a bunch of humour deprived pedantic morons inhabit forums of all types." QFT
Well done! At least you manage to quote yourself correctly. That's a step in the right direction. Keep plugging at it and I'm sure you'll have it all figured out someday by the time you're all grown up.
What are your ideas of good chess manners? I know about common courtesty but what counts as good manners for you when you're playing a game between friends and playing in a tournament?