Here is a simple trick to safe between 10 and 20 minutes per round of golf.
When you exit the green you have just played, keep you clubs in your hand and do not mark down your score.
When you arrive at the next tee you will have plenty of time to put your clubs away and mark your score. You have just saved between 30 and 60 seconds. Due this for 18 holes and look at the time you just saved.