Not sure if your asking how not to get caught by other people when collecting it or if your worried about spirits.
If it’s the former, make sure no one is looking and be very quick about it, If there is sod use a knife and cut a C pattern in the ground, pull it back then scoop out the dirt, best to do it that way, so once you put the sod back it should look like the ground has not been disturbed.
If the latter it’s always a good idea to leave a silver coin at the grave once your done, and store it in metal when not in use, if you don’t have a box of some kind then wrap it in aluminum foil, that will keep any lingering negative energy from oozing into your home.