You've graduated. You have your special piece of paper. Your CV is in order and you've got a letter of recommendation. And you have a contract! Dress carefully on your first day. After all, you're the teacher now, not the student.
You'll find heaps of ideas regarding classroom management on Pinterest and teaching websites, but I'm a fan of keeping it simple. Basically, it boils down to this:
you're the boss.
Establishing discipline is of utmost importance. You can't have a good, productive time with your class if they're out of control! Get a copy of the school rules. You don't want your rules to go against these. I get my students to suggest classroom rules during the first week. We write them down on the board and vote to accept them. If the student suggests a rule in the negative ("don't be noisy"), I elicit a positive language alternative ("be quiet"). I also number the rules. Then, when one is being broken, I can say "rule number 4!" or, "are we following rule 4?". Then I put them on a poster board to post in the room (the students often want to help decorate it).
You can have a time-out space if someone is particularly naughty. Sometimes, though, kids just need to move around. If my whole class seems antsy, I encourage them to move around (in a controlled manner - I am the boss, after all!). It goes like this:
Stand up! Reach for the sky. Shake your hands, touch the floor, turn around, jump three times, wiggle, take a deep breath, relax, focus on me, sit back down. They will love it and you will regain control.
Kids are kids, and sometimes they're bad by accident. Is a punishment necessary? Evaluate the behaviour and decide whether the kid just annoys you or if they've done something wrong. Was it intentional? If not, use it as a teaching moment. Correct the behaviour and let the class know it's not appropriate.
Kids are kids, and that means sometimes they're bad on purpose. Find out the procedure for dealing with inappropriate behaviour. Can you send them to the office? Is their a teacher on hall-duty who can help you?
I like to go in assuming everyone will be well-behaved. Students are at school to learn, after all. So I don't give privileges or rewards for good behaviour*, I take them away for bad behaviour. Students shouldn't have to earn fun classes. Games are not bribes, but part of the regular routine. Points can be lost. A fun activity can be stopped. Songs and videos can be turned off.
*I do believe in rewarding hard work. Improved students, an extra-attentive class, a project done to the 9s... these are all sticker or small prize deserving moments.
Don't worry about whether your students like you. Starting as the summer school teacher can be hard, because, let's face it, not many kids want to be in school in the summer, but it is also a good way to get to know people really well. My summer school experiences have been positive - smaller class numbers, more one-to-one time, more tailored class plans, ease of seeing difficulties, and discovering some "bad" students really just needed a change of pace.
You'll figure it out on your own, but hopefully my experience will help get you started.
And when you find something that really works for you, share it!