Here are some common mistakes done by new referees (and sometimes not so new :-))
Arrive to your game 20 minutes early: referees not only set the example but have many duties before the game starts. Including the duty of starting the game on time!
Keep your referee shirt tucked in your black shorts: even Youth referees have to do that!
Check that goal posts are aligned with the goal line: check that the goals are anchored too. The posts will help the AR determine if the ball completely crosses the line.
Pay attention to untied shoe laces: remind players before the game. During the game ask them to stop and tie their shoe laces (or to get help on the sideline for younger players)
Whistle more loudly:
Don’t be afraid to use your whistle so that all players hear you! Your whistle signals must be loud and consistent. Check with ARs or coaches if it is loud enough.
Do not whistle to signal a restart when the ball is already out of play: you don’t need to whistle for a thrown in, goal kick or corner kick. In particular you don’t need to whistle to signal a goal. The only time you should whistle to signal that the ball was out of play if it wasn’t obvious, the ball came back on the field or players kept playing.
Do not keep game cards in your hands: whether you are CR or AR, running with a piece of paper in your hand is not practical and doesn’t look good Take the time to put the card back in your pocket. You either have a whistle or a flag in your hands.
AR, stop before doing a flag signal:
Don’t wave the flag while running. First stop, face the field and do the proper flag signal. Also switch to the correct hand, do not cross your arm in front of your face to signal the other direction, it looks bad!
AR, focus on your offside line first: it’s tempting to watch the game and forget to stay aligned with the 2nd to last defender!
AR, demand space on your line: do not step on the field when people are obstructing your path on the line. Ask everyone to give you a 2 yards clearance!
Check the game cards before leaving the field: verify that cards were filled out correctly (absents, subtitutions, goal scorer, goal keeper. Count the number of active players in each period). See the coach if any data is missing. When at home remember to enter the game cards in WebYouthSoccer before the end of the week-end.
Talk to your fellow referees: The best way to learn is to talk to the other referees on the field at half time and at the end of the game.
Report problems/ask questions: The 2nd best way to learn is to ask questions later to a larger group or your RRA (pizza night, emails, etc.)
Do not wash your referee patch with the shirt: your badge is glued to a velcro, the glue may not last long if you forget to take it off.
Finally, do not worry about making mistakes during your match! After a possible mistake move on and stay focus on keeping the game Fair, Fun and Safe. Experienced referees make mistakes at each level but they are not as easy to see