I haven't experienced anyone telling me I was not posting right or did anything wrong in the game I was playing so I must be doing something right *wink*.
I read some of the intros before I came here, loads of warnings and edits were made. When we used to be in the Role-playing Games I don't recall us having these issues must be a new batch of players with milk on their cheeks still. So what if someone tells you to post properly or in the right place its not like they're asking you to turn over your bank account. Get a grip and move on, there are so many bigger things in life than your little center of the universe opinion.
I think this is an Etiquette issue so I will post it here. If the moderators think it needs its own thread I can do that.
But another rule I try to abide by, both around the table and in play by email/post games, is to learn the basic rules. And the rules for the class/type of character I am playing. Now obviously, especially when starting in a new game, everyone makes mistakes, and the GM is there to correct misinterpretations of the rules. But especially in post/email games, it can slow things down even more.
I certainly ask my Game Masters/Dungeon Masters about how things work, even in games whose rules I feel fairly comfortable that I know. And I still make my share of mistakes, but too often I see people who have been in a game for a fair bit and they still make mistakes that totally ignore the rules. It tends to drive me nuts. I frequently want to do more than the rules allow, but the rules exist for reasons, one of which is to balance things so everyone can contribute…
It's hard to play when there is someone on the team who doesn't know the rules well, if at all, but that is a normal thing when you bring a new player into the game. There will be a lot of hand-holding and patient instruction of newbies, and that is also part of the Role-playing Game world. A lot of times, people hop into a game system with no clue what they can or cannot do, and us old fogies have to spend the time and edumacate them until it goes smooth. :D.
I think its up to each Dungeon Master to decide how much you should know before playing. If you are looking for players there may be a strong temptation to take on anyone but in the long [run?] it might not pay off so well because you have to use so much play time to 'explain the rules' time which can be frustrating.
I think it's okay not to know a system well, so long as the player is willing to take feedback about any missteps they have made and then take the effort not to repeat the same mistakes.
The thing that I think is most important for etiquette is that players and game masters have to be clear about what their expectations are for each other, and to make a good faith effort to abide. This will vary wildly from group to group and is an important thing.
The expectations should come from clearly written rules from the Dungeon Master. If you run a game that is not properly organized the play style will be out of sync and more time will be spent on what everyone should be doing than playing.
If you're sitting down to play a game I'd expect you to have the same manners you would have playing any other game or what's expected. "Please", "Thank you" and other golden words can go a long way no matter the situation.