Keep yours hands up and watch his body, don't stare at his head but no where it is. Be aggressive, but alert. Have fun.
Besides just boxing, do some weight training and do some exercies that uses your own weight such as pushups and pullups.
Work on triceps, your chest and your abs for stronger punches. Your body is where the power of your punch comes from, not your arms. Learn how to punch and avoid punches before boxing.