Make meetings a priority. Attend regularly and be on time. Be an active participant. Set positive goals and work toward them.
Keep your expectations realistic. Look for improvement, not miracles. Give as well as receive.
Keep the group in its place. It's possible you will make friends within the group, but don't depend on members and meetings for your social life.
Play by the rules. Avoid making criticisms or forcing advice onto the group. Listen more than you talk.