My favorite softball warm-up drill at the start of practice is to have half the players at the pitchers mound (for 8U girls) or at the short stop position (for 10U girls) and the other half at first base.

Softball Warm-Up Drill
I stand at home plate.
The pitchers mound/shortstop girls field the ball from me and then throw to first.
The next girl in each line is the outfielder backing up the fielder.

Once we’ve done a few minutes of this, I take two players at a time and make them base runners (they alternate) who have to try to get to first before the fielders can throw them out.

I make the base runners start at the backstop fence farthest from first base.
I’ll let the base runners go two or three times each and then cycle through new base runners until everyone has had a turn.   If there is an odd number of players, I’ll be a base runner.

Coaching Throwing Tip
I make the girls throw 50 good throws in a row (without the ball touching the ground).   I use that to keep their concentration up.   During games as we approach the last few outs, I remind them by saying “this is like throw #45 – keep your focus!”.   This helps them concentrate through the end of the game.