Explain the concepts of teams and innings. In baseball, two teams play until a winner is determined. Each team gets a turn at bat. The "visiting" team bats first, and the "home" team bats second. After each team has batted once, an "inning" had been completed. Explain that the major leagues play nine innings, but kids play six innings. At the end of the game, the team with the most runs is the winner.
Explain balls, strikes and outs. Inform the kids that the team who is batting is on offense. When a pitch is thrown, the hitter has two choices -- swing or not swing (take the pitch). If he swings and misses, it's a strike. If he hits successfully, he goes to first base. If he takes the pitch, it's up to the umpire to determine if it's a ball or strike based on the strike zone. If he receives four balls before making an out, then he gets to "walk" to first base. If he accumulates three strikes, he's out. Also inform the players there are three outs for each team each inning.
Instruct the kids about fair and foul territory. Talk about how when the batter hits the baseball, it must travel between the lines in front of home plate. If it does, the batter must run toward first base. If it goes behind those lines, it is a foul ball. Explain that a foul ball counts as a strike. However, if a player has two strikes and fouls the ball off again, she is allowed to continue to hit until she hits the ball in fair territory, strikes out or receives a walk.
Explain the difference between ground balls and balls caught in the air. Instruct the players that if the ball is hit on the ground, the defense must field the ball and throw it toward a base where a runner is heading. If the baseball is hit in the air in the form of a line drive or fly-out, then the defense must catch it in the air to record the out.
Cover base running. Players must run around the bases in order (first, second, third and home) to score a run. Explain that while at bat, if a player hits the ball into fair territory, he must run to first. Players on any other base must run only if a player is on the base behind them and the ball is hit on the ground in fair territory. However, if the ball is hit in the air, a player on base should move only if he does not think the baseball will be caught. Also, if there is no one on the base before him, he is not "forced" to run. If the baseball is hit on the ground, he should run to the next base only if he thinks he can make it. If the ball is hit in the air, he should wait to see if it is caught. The exception is when there are two outs and the ball is hit -- then everyone runs to the next base.