If you are quick with your hands you will make it easier on yourself to throw out runners that are trying to advance to the next base. Let's start with fielding a ground ball your hand should be placed above the glove hand when approaching the ball. This allows you to field the ground ball pull the hands in to the body and get to the throwing motion quicker. If your hand are not in position, that fraction of a second it takes to get them there after fielding the ball is all the time needed for the batter to beat out the base hit.
When fielding a fly ball in the outfield hand position is just as important. As you approach the ball you hand should be right beside the glove so that you can transfer the ball to your throwing hand with little to no wasted movement. This gives you the seconds needed to throw out the runners from the outfield.
So work on getting your hands where they need to be to make a quicker transfer of the baseball. a drill that you can do is stand a couple for feet away from a partner. Take a baseball and roll it or flip it to your partner. As you catch the ball work on your hand position and getting the ball to the throwing hand as quickly as possible. Then move to catching ground balls and fly balls and hand position as well. I leave you with this fundamentals is the key to great players. If you are fundamentally correct in every facet of the game you will turn some heads.