If you want to swing a sledgehammer, pick it up with the weaker hand and hold it closer to the head using the dominant hand. A vertical swing may necessitate you standing directly in front of the target while a diagonal swing is best done from the side. Lift the sledgehammer on the dominant side to the level of your head and drive it down into the target. While at it, ensure the dominant hand is directing the sledgehammer as the non-dominant hand adds to the weight.