As all have said welcome to the forum.
Sometimes I look back on my first years and it is a wonder I was not run out of town.
It will take time to get into your groove dont get disheartened.
Let me throw a few things your way and take them, as you will
Every game you do will not your best but strive to make the next one your best.
You are not doing Duke Vs Kentucky but to the kids the game is just as important. Stay alert and dont let self -doubt set in until after the game. When you are along then go over the game in your mind with the rule and casebooks at your side.
Though I do not do this enough and I know I should One of the instructors for our association preaches that one should keep a dairy of every game we do. What we did right, wrong, and what we saw.
You will hear a 100 times to slow down, I like to call it one step at a time. Whistle, hand/fist up, sign or direction are three individual actions so make them so.
If it is a foul, before you make your move the reporting area take a breath and make sure you know the number of the offender and the shooter if it is to be a foul shot. Let your partner know what is going on so he or she can set up the shot or inbounds as you are reporting to the table.
Be it a rec game or a middle school game treat it like your associations BOD is sitting in the stands. Make sure you do the proper switching. If you dont reinforce it now you will have trouble in the future (Take it from one who knows first hand.)
You dont know everything and you never will. (As in my post on Saturday) Dont be afraid to ask questions, either here or a more experienced ref. Take the answers, weigh them and find the best for you.
Coming from a rec league background I feel it is extremely important that you do such low level games. These include middle schools and elementary schools if they play in your area. This said for 2 reasons. One is that you will see more fouls per game at these levels than you can count. This is a very, very, very good way to learn advantage/disadvantage. The other is that you teach the kids what is allowed and not allowed.
Remember, it is called a Basketball Game so have fun.