When my oldest was four, a friend convinced me to coach T-ball with him. I signed up to coach and quickly realized there's no real attention span for kids, parents think it's major league ball, and some kids will just pick grass the entire time. Fast forward four years, and not much has changed.
Regardless of the sport, I've learned a few things about coaching my kid and others. The first, don't over-coach your kid. I see this all the time, coaches either let their kid play whatever position they want, over-estimate skills or they are toughest on their own child. I'm hard on my kid in a supportive way, and I try and do that for all the kids. Encouragement is king, it works well for failure, "you'll get it next time" or "that's the way!" And all kids play all positions! Especially with younger children, the only way to get better is to play and try different spots on the field. I used an excel spreadsheet to make sure throughout the game and season kids get to try everything several times. Sometimes it's painful to watch, especially if your child struggles, but eventually, they get better.
Teaching kids proper form, where they need to line up, how to guard someone, comes natural to some kids but not everyone. If a child doesn't listen to me, which happens, I try and have another coach, parent, or one of their peers tell them. Since we live in the digital age, I've told parents to watch YouTube videos of shooting form or game rules. I also repeat things a lot, because listening is hard, especially for kids.
Agility helps with all sports, however, that does not mean you need to work on running over hurdles or shuffling over an agility ladder at seven years old. Concentrate on sport-specific drills like running and dribbling a basketball, catching a baseball with your glove instead of hand, or passing a soccer ball accurately. Last year I set up a little obstacle course for my soccer kids. A few could use the agility ladder and hurdles but most were tripping. I think for high school or junior high kids these tools would work well. I thought it would be fun for the kids, which is key.
Playing a sport should be fun! Barking at your kids on the sideline often removes the fun. How are your kids going to learn to keep their hands up if you yell it the entire game? And remember what I said about attention spans, imagine you're yelling at your kid, the coach is yelling at the kids, who do they hear? No one. I'm all for yelling "Nice shot" or "Way to go" but let the coaches coach. Your kid will figure it out.
I also try not to make a big deal about winning or losing. Kids pick up being a poor sport early. My son's basketball team won all their games and lost all their playoff games. The first playoff loss, we went for ice cream, because win or lose, there's always ice cream. The team he just played, filled with his friends, ended up joining us and they had a great time laughing together.
Before sports becomes super competitive, with try-outs, benching and over-coaching, just be happy your kids are having fun and not behind a screen.