Play with friends.
Let everyone know you are new.
Get to know the rules, and be open to constructive criticism. If the DM corrects you on a rule or roll, just go with it.
Do what you can to help the game flow. Don't sit at the armor shop for thirty minutes trying to haggle the price down by 5 silver while everyone waits around for you.
Be a TEAM PLAYER. Your character can be an individual, but still do what is best for the group.
Occasionally a session will 'feature' another player over the rest of the group. Understand this. Willingly help out the Paladin in their quest to earn their first Holy Warhorse, and the favor will come around to you when you need help avenging your mother's death (or whatever character-specific adventure you might need help with).