I've been going to children's athletic games for years. Football, basketball, volleyball, soccer, lacrosse, etc. Maybe the most annoying thing that makes it much less enjoyable for everyone is that one out-of-control parent that constantly yells and complains at refs, players & others around them.
A few thoughts:
1. Don’t coach unless you are the coach
If you want to coach, volunteer to be one. Otherwise, leave the coaching to the parent who did volunteer to coach your child’s team.
2. Leave the refs alone
You’re either embarrassing your child or your teaching them that yelling, cursing at, and harassing the referees is the way to get your point across. It’s not.
3. Quit yelling / Complaining to refs - players - coaches
It only causes tension and annoyance and everyone around you just wants you to be quiet.
4. Support, don’t criticize
Know the difference between saying “Nice try!” versus “You have to be faster to the ball!” One is going to encourage your child, the other will leave them feeling dejected.
5. Remember who’s playing the game
It’s not you. Your previous sports experience is completely irrelevant when your child is on the field and you’re on the sidelines.
6. Emphasize fun and enjoyment of playing the game, not winning
This is youth sports, not the pros. A win shouldn’t make or break the mood for the day.
7. Enjoy your child’s play
Even without a fantastic shot, your child’s play should be fun to watch. Just enjoy it. Make sure they know that. Some day, they'll be gone and it will all be over.