And let's not forget one of my pet peeves... The pitcher must make a complete stop with the ball in front of the body for at a minimum of 1 second before starting his/her delivery.
There's also no "leading off" on the bases.
On a caught fly ball, runners must tag up. If the catch is bobbled, they must tag up after it's first TOUCHED, not when it's caught.
On an uncaught infield fly, runners do NOT have to tag up and they MAY advance.
Defensive players not in possession of the ball OR in the act of fielding a BATTED ball must let the runners by without obstructing them. In other words, "get out of the way!"
Report all of your substitutions to the home plate umpire. Remember, a substitution occurs as SOON as you put them in. It's not "well, I'll report it when that player goes out to play on defense." Report it as soon as you make the switch.
Keep your batting order straight. Batting out of order creates a big mess that no one likes to sort through.
Last but not least: respect the umpires. If you come off as a jerk, you'll have a long season. You're human, we're human. If you accept the fact that everyone is out there to do their best (including umpires), you'll have a lot of fun.