When I work on this play with infielders, especially those just starting out, I usually do it in steps. It starts off very easy in order to learn and get comfortable with the footwork and gets progressively harder and more game-like.
Step 1. Ball in the gloveHave the player start with the ball already in his glove. This allows the player to focus all his attention on the footwork. Now have the player extend his left foot and glove out in front as if he just caught a waist high chopper. Have him freeze this position. This shows the player where his left foot and hands should be when the ball is caught. From here, when the coach says "go," the player should step forward with his right foot and throw the ball off that foot. Keep in mind the arm angles mentioned in Part 1.
Step 2. Lob a ball then roll the ballNext, stand a few feet away from the player who is in the beginning position above (hands out, left foot forward, standing still). Now lob a ball waist high. After he catches the ball, the player steps forward with his right foot and tosses the ball. Continue this step by using a variety of heights on the lobs as well as introducing ground balls.
Step 3. Two-step timing
This time, have the player stand with both feet together. When the ball is tossed to him, he should step forward with his left foot to catch the ball. He should time it so the left foot lands at the same time the ball is caught. The player then steps forward with the right foot to throw. The coach can once again use all types of ground balls to force the player to practice multiple heights of catching and throwing.
Step 4. Game likeIn this step, a coach can roll, bounce, or hit balls from a farther distance to mimic game-like conditions. Players should start slowly to practice the footwork and timing and gradually move faster to and through the ball as they get more comfortable with the mechanics.
Step 5. VariationsWhen the player has the footwork and timing down pretty well, a coach can then roll or hit some slow rollers to the player's left or right to make the play more challenging.
Step 6. Get out the stopwatch
Figure out what a fast running time from home to first is for your level. Hit slow rollers and have someone time the play using a stopwatch. Start the stopwatch at contact and stop it when the ball is caught by the first baseman. Continue drilling until the fielder consistently gets the ball to first base under the running time.
Although this is one of the toughest plays in baseball, players at almost any age can learn the proper mechanics and drill to become better. These drills are great for indoor practices because you do not need a lot of space and gym floors provide a safe, no-bad-hop surface in which to train.