Whats't the best way?
Straight rubbing alcohol or straight vinegar. Alcohol will also make your faucets etc SHINE!!!!
Dawn and vinegar mixed. It will take off all hard water stains. Make sure you purchase the Dawn at the grocery store, it is thicker than the dollar store kind. Use a microfiber cloth to clean. Rinse well. After you get it clean do this weekly. Also dry your door after each shower with a towel. You will no longer have problems.