Take a look at the [tag]softball throwing drills[/tag] below. It is a [tag]softball drill[/tag] called “line ’em up!” A great example of a drill for run-downs that can work with all age groups. 
Split the team in half and line up one half behind 2nd, facing first, and the other half behind first facing second. No runner. Start the players in an imaginary run-down. A couple lines drawn in the dirt will be where they need to get rid of the [tag]softball[/tag]. Make sure they don’t fake throws as they will only fake out their teammate. Also make sure they are on the correct side of the baseline. After the throw, the thrower gets into the opposite line. See how long they can keep the drill going with everything correct. The drill is over when the ball hits the ground.
After the softball drill I take a break and tell the players how to run a player into only one throw but now we know we can make more than one throw if necessary.