1) It will be hot! Take hydration breaks especially in the afternoon. Ask the coaches in pre game. 

2) Check player cards. Everyone should have them.

3) Run with the play! Don’t be a “center circle” ref and make sure if you are the center, run the field. Kids, coaches and parents will appreciate your energy and your close up viewpoint. You want to be neither too close nor too far from the action: 10-12 yards is a good rule of thumb. If you are the AR, run along the touchline, between the halfway line and the goal line, keeping level with the 2nd-to-last-defender or the ball, whichever is closer to the goal line. Keep up! 
4) Have Fun! Have Fun!