Read the rules and get acquainted with them. Obtain a copy of the rules and keep it in your dorm room.
Keep your music low to ensure no one complains. Even if it's the middle of the day, someone might try to sleep or study. Know when quiet hours are to be sure you're going by the rules.
Know the policy on opposite gender guests. Some dorms may be coed, while others are same gender; the opposite gender may not be allowed in the dorm or they may need to leave by a certain time.
Follow the dorm rules on alcohol. Even if you're of the legal drinking age, you may not be able to have alcohol in your room because of the danger of underage drinking.
Acknowledge where smoking is allowed. Many colleges have designated areas where you may smoke, though this is increasingly only allowed outside.
Refrain from using appliances or other things that are a fire hazard. Items including candles, halogen lamps, portable heating units and hot pots can be dangerous when you use them in a dorm room, especially if you're not carefully supervising them.
Take responsibility for your guests. Even though they're probably capable of taking care of themselves, you'll be held responsible for anything they do.