He may have played a long time but I would have him read over Laws 11 and 12 before each weekend. Law 11 is offside. Law 12 is Fouls and Misconduct. Most leagues/coaches do not expect refs to give yellow cards and Red cards at U10 but you should know when they should have been given so you can teach the kids. "Hey, a little older and that's a yellow card for Stopping a Promising attack." or "A little older and that's a Red card for DOGSO" or whatever. And for some reason, so many players, coaches, parents, etc struggle with the "pass back rule". Remember that the ball needs to be DELIBERATELY KICKED TO THE KEEPER for it it be a indirect kick. At U10, kids are just kicking it and sometimes they try to clear the ball and the keeper runs and grabs it. That's not a pass back. A kid tries to pass it to the teammate and it goes to the keeper. That's not a pass back. If it's not 100% obvious that the player was deliberately kicking the ball to his keeper, it's not a pass back.

Another thought... At this age, talk to the coaches before the game about throw ins. Does each kid get a redo? Two redos? Unlimited redos? One redo per half Two? None. Figure that out before the game and, if it's hot, discuss water breaks with the coaches too.

U10. Remember to know the build out line rules and there is no heading so know the restarts for deliberate and accidental headers.

And don’t let the kids talk you out of a call.

We had one team try to talk the ref out of a goal we scored because the ball had gone in the goal and through a hole in the net to the other side. The opposing team argued that we hadn’t scored since the ball was outside the net; the ref was going to reverse the goal until one of the coaches walked over and demonstrated that the bottom of the net was not attached to the goal. After the fact, it was pretty amusing (these U10s can be pretty loud and convincing) but our players would have been indignant if the goal had been reversed.

DD is 16 and did this past weekend. Talk to the coaches real quick at the beginning. Check the kids in. U10 is still super young so you'll get kids of levels of ability and levels of interest. He'll spend alot of time making sure they move back during goal kicks and free kicks. Know the rules and make the obvious calls. Ignore any loud parents. At that age there won't be many, but depending on how many games your son is reffing he may encounter one at some point. After he has a few games under his belt he'll be comfortable. Lastly, tell him to be confident. With no AR's, it's not always easy to see everything when the kids get all bunched up. Tell him to call it as he sees it and stick to it.

Very good advice from above.
My son started reffing at that age, and as an experinced player, he let too much physical play go when he started then he should have. Call things tight with the young kids!
And yes, get to doing three man games ASAP, but very few assignors will give kids centers until they do a bunch of games for U-littles. Again, talk to your assignor to see what the path will be.
Mentor, mentor, mentor! I've reffed for decades, so I helped my son, but try to get someone watching whenever possible. If someone can record the game, even better.
In the end, it's so much about exuding confidence. Make every calls as if you've never been more sure of anything in your life. Players/coaches/parents can detect weakness, and will yell far more if they see you as hesitant.
Best of luck! It's hard, but rewarding, plus at that age the pay is spectacular.

These are great tips - thanks! Keep 'em coming (15 year old kid has been an AR but not a center ref yet; has played club soccer for 7 years; knows the game so hopefully will be fine, but doesn't want to forget/miss anything!)

Well I'm not sure how much experience you have in general as an AR or even as a player so it's tough to know what level of details you need, but my first thoughts are....

I do not like reffing with no ARs so I look for leagues that use ARs at even U11 or U12. It's not easy watching both sidelines, both goal lines, offside, etc. But you are doing it so good luck. Read over the Rules of Competition the night before. There are the overarching Laws of the Game but each league have their Rules of Competition that overrule the Laws of the Game. Rules of Competition covers...length of halves, substitution rules, check procedures, where parents and players should sit, how many coaches are allowed on the bench, number of players on the field, game report procedures, mercy rule or not, etc. etc. etc. Game Day. First, dress the part. Wear the correct socks, shorts, shoes, hat, don't wear bling, wear two watches. Have the correct badge on. Look confident. I use a fitbit that counts down and then I use a watch that counts up. I've had a watch stop many times for various reasons, so two watches is helpful. I also keep a spare pen in my sock. Sometimes your pen runs out of ink at inopportune times. Get to the field 30 minutes before. Check the field for and safety hazards. Holes. Grass. rocks. etc. Check the goals. Do they need more sandbags? Holes in the net, etc. Corner flags.

Start checking in the players once it looks like they have the full team there. Hopefully, 15 minutes prior. Talk to the coaches and verify Rules of Competition. About 5 minutes to kick off. Call Captains. Make sure you have a coin. You should also have yellow and red card. Note book to keep score. Pen. Whistle.

As to the check in procedures...it depends on the league. Some require that teams have player cards but you only need to do a safety check. Some require you to go through the roster and check player cards. But worse case scenario is that the team manager hands you a binder of player cards and a printed roster. You can ask the team manager to help. But you can call the name, verify number, and check picture on the game card. Go down the list. Rules of Competition tells you what "mistakes" are allowed on the roster.

Do's and don'ts. Again, no idea of the level you are reffing, but probably the most important thing with reffing U10s is parents want you to protect their kids. Start the game off by calling it "tight"...meaning, if border line, call the foul. See how the game progresses and feel free to "loosen up" if the kids are OK with the physicality of the game. In otherwords, if you call a soft foul and everyone is upset, maybe loosen up a little. If everyone is yelling to protect the kids, tighten up. At U10, it's a small field so stay close to the play. Helps with match control and you selling your calls. Don't be a ref that stands in the center circle. Run!

Ask your assignor if there is a mentor available to come out and watch and give you feedback.

If you any other Qs, fire away.

Any veteran refs out there have a checklist/tips for a new center ref - will be referee for a U10 game (so no ARs)? Dos and Don'ts/things to remember? 1. get game card from manager; 2. player check in/off; 3. start game/set timer on watch . . .

Any thoughts appreciated