1: Be Attentive to the DM.
When the DM is telling the story or progressing the encounter, do not interrupt nor talk. We come together to play D&D, when the game flow is interrupted with talking, the immersion is lost and people can get distracted missing important parts.
2: Don’t talk when other players are talking.
When it is someone’s turn in the initiative or role-playing, do not interrupt nor talk. Everyone wants their time to play their character, don’t steal that from them.
3: Know your character.
Don’t rely on others to tell you what your abilities do. You do not need to know the full Player’s Handbook, but you should know the parts that pertain to your character at the level you are currently. Print your spells or get spell cards if you are having trouble remembering.
4: Let players play.
Let players play their character the way they want to play them. Allow them to make “mistakes” and learn. Yes, talk about your plan of attack, but allow players to make their own decisions.
5: Minimal to No Meta-gaming.
Please keep “out of character” or “out of game” actions to a minimum. Try not to make use of knowledge that you, as a player, may be aware of but the character you are playing is not meant to be aware of. Sometimes a break is needed to pull thoughts together, but make sure the timing is right, and ask the DM for the opportunity to do so.
6: Don’t Upstage. Share the Spotlight.
Don’t always be the first to talk. Look for opportunities to help others shine. Try to work with others to make really epic moments that everyone can take part. If everyone has this mindset, your moment to shine will come. Never say “You stole my kill” or “I was going to do that”, that is not fair to other player who can also see what is needed for the encounters. This is a team game, when the team wins, you win, when the team fails, you also fail.
7: Don’t Not Discourage Other’s Ideas
Don’t tell people that their ideas are dumb, stupid or won’t work. The DM is telling the story or progressing the encounter, the DM will decide weather or not a Players ideas will or will not work.