The putting green, overall, is typically a relatively flat surface and we want to allow the surface to remain as pristine as it was when the greens staff worked on it in the morning throughout the day.
One of the easiest and best things you can do to ensure this is to always keep a repair tool in your bag and remember to repair your ball mark, plus one more if you can, on every green.
Be mindful of your feet and how you’re walking on the putting surface. Even with soft spikes and spikeless shoes, dragging your feet can leave the putting green a little worse for the wear. Similarly, be sure to walk normally on the surface; running or even standing in the same place for an extended period of time can create depressions in the green that will make it difficult for balls to roll true.
Finally, pay attention to what you’re doing when you’re removing and replacing the flagstick. If you become careless doing this rudimentary action, you could damage the green right around the hole or even the cut of the hole itself.