The beginning of competitive softball begins in the 10U leagues, where winning and losing starts to make a difference. Lower league ages are more for fun than anything else, where as the higher youth ages signal the start where competition takes over. This doesn't mean that 10U softball should not be fun for the entire team, but actual training and discipline begins here that will carry over as the player gets older and more proficient.
Your best player goes here. They have to be just as adept at grounders as they are with pop flys. Position them about 3 feet off the line, and about 5 feet in front of the bag.
Catching the ball here is paramount, because there are going to be a lot of balls thrown for "outs" in their direction, so this person must have the surest glove on the team. Practice consists mainly of lightly hit or thrown grounders, from you and teammates, making sure with every toss that they tag the bag.
At 10U, you can almost consider the right fielder as an extension of the first baseman. This is actually a deep infield position with the main purpose of this fielder to back up the first baseman. They have to have a pretty good arm.
Practice must include grounders thrown or hit to the right fielder, who then makes a sharp throw to first. This includes ground balls hit down the line past first that the right fielder needs to cover.
This is the most athletic position on the field, and the 3rd baseman is responsible for all balls hit to that side of the field, particularly bunts.
The 3rd baseman must be fleet of foot and have an arm that can get the ball to the first baseman. Practice should mainly consist of grounders and the accurate throw to first. And make sure the grounders are all over the field on the 3rd base side.
Essentially, 2nd base must plug the gap and not allow any balls to get into the outfield. So ball presence and awareness is a must at this position. Since they are going to be the closest fielder to 1st, they don't need the best arm, but the throws need to be accurate. Practice fast grounders on each side so that, even if they don't pick them up, they get in front of them and stop them from getting away. Then, incorporate easy tosses to 1st for the out.
10U is also the the year when the "double play" may actually have potential to be pulled off between the 2nd and 1st baseman. But at this point, forget it. It's too complex, and basic fielding techniques trump any double play scenario. You may want to gingerly walk your players through it, but pulling one off is not high priority at this level.
Although this is generally where the best player goes in most other age groups, in 10U, you can take one of your least talented players and put them at short.
The reason here is this. Balls straight up the middle will be handled by the pitcher, and any other ground or popped ball to the pitchers right will be handled by the 3rd baseman. Essentially, the shortstop is plugging a very small hole.
Practice consists of grounders, pop flys and throwing to 1st. Make sure they get their proper defensive reps, but don't hold your breath.
The right fielder backs up 1st, and both the left and center fielder must not allow the ball to get past them, no matter what, or it will invariably turn into a home run.
In 10U, there are still not going to be very many deep fly balls, so the outfielders need to play only moderately deep. Their main purpose is to get the balls that make it past the infielders, and most of the time, the balls that get out there won't have a lot of mustard behind them.
Practice includes throwing and catching with the infielders, making sure the infielders throw the ball on the ground while the outfielders pick it up and throw it back. This mimics what will happen in a real game.
Some 10U leagues don't play a catcher, but if yours does, this is the place where your player with the least amount of defensive talent will play.
Don't Expect Miracles
10U is still pretty young, but this is the age when real talent will begin to show, and it's up to you, as a coach, to find it, get it to where it belongs on the field, and give your team a genuine chance to win, while still making it fun to play!