If your shot causes a divot to be dislodged, walk over, pick it up and put it back. Be careful not to leave your shadow over the hole. Wrap your hand around the flag to keep it from flapping and loosen the flagstick slightly so you can pull it out after the putt is hit. Stand at arm's length. Be courteous to those behind you, especially if you already lost a ball earlier in the game.
Spiked shoes can tear the grass and leave gashes.
If the grass is very wet, the spikes will also leave holes in the surface of the green. A damaged course is not pleasant for other players. You should know where the other balls are so you don't step in the way of another player's putt. The best route to your own ball is to walk behind any other balls laying on the green. By fixing the mark, you will be ensuring that golfers who play behind you will have a smooth surface.