No matter what the sport, can you please quit doing these things:
Coaching at the game. Yelling from the sidelines and trying to out-coach the coach is confusing for everyone - and embarrassing for you, whether you realize it or not.
Making it all about you. Attempting to live out your own dreams through your child's sports participation places adult-sized load of stress on kids who are playing. Check your ego.
Having unrealistic expectations. Hate to break it to you: while 26 percent of sports parents in the U.S. hope their child will go pro, only about 1 in 168 high school baseball players get drafted to the majors, and just 1 in 2,451 high school boys basketball players make the NBA. This is - almost certainly - just for fun. Manage your expectations.
Forgetting coaches are volunteers. Most of the time, coaches are getting up at 6am and patiently running the kids through their billionth drill because they want to be there, not because they're getting paid the big bucks. Treat them accordingly.
Totally losing it when the coach yells. No, the coach is not raising his voice because he's a mean ogre looking to traumatize your baby. He's yelling (in most cases) because everyone on the field (or on the rink, or in the pool) needs to be able to hear.
Not apologizing if you get out of line. Coaches get it, for the most part: parents are passionate about the sports their kids play. But if you've stepped out of line, you need to apologize, then work to avoid making that mistake again.