As with any game there are specific courtesy rules associated with playing golf. The most important rule is to not disturb the person who is hitting the ball. It is rude to be talking, moving or standing too close to a golfer that is about to hit the ball. Think of watching golf on TV, the entire audience is silent when watching a player tee off.
You want to keep moving without any delays. Sometimes you may have to wait for the group in front of you but as soon as they are done you should continue on playing. Sometimes this can be difficult land if the group in front of you is particularly slow they should allow you to move in front of them.
If possible you should attempt to replace any divots and smooth and footprints you may leave in the bunkers. You also should never drop your clubs on the putting green as this area is leveled and smoothed for the purpose of putting.