Coaching hitting is difficult, no doubt about it. What I see most often is a general belief that more is better. More swings will result in a better swing. Kids are running around practice swinging the bat in different stations, trying to get as many swings in as possible. It's often a hurry up to get all kids up in batting practice and give them as many swings as possible. Over the years, I've modified my practices to emphasize quality of quantity. This takes a commitment by you as a coach to make sure hitting isn't a rushed part of practice.
One of the easiest ways to do this is have everything based on time, rather than number of swings. When you setup your stations, have each station run for 3 minutes for example. With 12 kids that would be a 36 minute batting practice. Then emphasize with your team that the goal is to have every swing be a quality swing and every swing has a purpose. If a player gets tired, take that station off and get ready to be productive at the next station.
As a coach try to set realistic goals for your team and each player. If you draft a Little League or Pony team and don't know much about your players. Don't have a goal at the beginning of the season that your team will hit .350 or .400 as a team. Your team may not have enough talent to come close to that.
Instead have your coaching goals be related to evaluating and making small adjustments for every player on your team (every player that needs it, some may not need much) in order to have him improve as a hitter throughout the season.