Know the airplane systems well.
Have at least a rough idea of takeoff and landing rolls. See how close to the published figures you can get.
Takeoff with full tanks, and check your estimated fuel burn the next time you fill the tanks.
Know the proper POH speeds for your aircraft and use them. Don't use some half-baked instructor nonsense like 80 knots on short final in a 172.
Work hard at situational awareness by listening to other people on frequency and strive to make clear, accurate and concise radio calls.
Be courteous and friendly to all people you meet. Someone may offer you a job, or some flying one day.