Make sure they know the situation and where to go with the ball when it is hit. Whenever a runner is on third base, it is the pitcher's responsibility to cover home on any ball that goes by the catcher. Never barehand the ball unless it has come to a complete stop. Get that first strike in on the batter. This gives the pitcher a tremendous advantage to be ahead in the count.
Walks are poison.
Not only do they give the opposition baserunners, but walks tax your player's arm and bore their defensive teammates to death. Let them hit it. The odds are in favor of the defense 9 to 1 when the ball goes into play. Coaches count pitches. Particularly early in the season.