1) Do not spend all of your time revising
Yes, okay, exams are important. But they aren't the be all and end all. Yes, you will need to sacrifice some of your time to revise and do well in your exams, but don't forget that it is also important that you make memories with your friends as well as do well in your exams.
2) Peer pressure doesn't really happen as much as you'd think
I've been asked a few times why I don't drink when out on a Friday, and I have simply said "because that doesn't appeal to me", and people have either left it there or they have said "you should give it a try" and left it at that. It hasn't really impacted me that much.
3) Work in your lessons
It's easy to get lost in conversation in school, but don't do it too often. The more you get done in class, the less you will have to do at home.
4) Don't Procrastinate
Everybody says that you should do your homework the night that you get it, and that's not necessarily true, but you shouldn't leave it to the last minute either. Do it when you have time, but try to do it with time to spare, so you on't have to stress about it. Procrastination is awful, so don't fall into the habit of it.
5) Enjoy it!!
I left school 2 days ago, and I want to go back. luckily, I get to go to another school. You will miss school when you leave. And it sounds unbelievable, but it's true.