If it relatively shallow 2-3 inches I just use a probe and locate the item and then back off of it and pop it up. For deeper items I think a plug is the best. Pinpointing the item is critical. Try to keep the dirt in the hole and then replace the plug. I am always concerned how it looks but go back a day or two later and you can't even tell anyone was there.
If you have to cut a plug....ensure that you ONLY cut three sides and leave it hinged to the ground. This will ensure that the grass doesn't die in that spot and it will reduce the chances of a lawnmower picking up the plug. Remember...if we leave the grounds a mess...chances are we won't be welcome to detect another day. For the sake of our hobby respect the areas you detect.