Don't press the meat together too hard. Don't flatten burgers with the spatula. It presses the juices out of them. Use the spatula to turn them only. Insert the instant read thermometer into the side of the burger to get the proper temperature reading.
Medium coals are best for burgers.
If the grill is too hot, the outside will burn, and the inside will be rare. Bugers tend to plump up when on the grill. To make flat burgers, after you make the patty, make an indentation in the center of it with your thumb. Rotisserie Place an aluminum pan under the meat. Make sure there is water in the pan.