1. That first lesson
Enjoy it! Sure, it'll be nerve wracking and you'll probably make a mistake or two, but you only get to teach a lesson for the first time once. The kids will know you're a trainee so don't worry about trying to hide the fact that you're a rookie. Be yourself, the kids will know if you're pretending to be someone you're not and won't respect you.
2. Don't worry if the kids don't like you
You're not there to be their BFF, you're there to make sure they learn. That's not to say you can't get to know them, they'll respond much better to you if you ask them if they won their school hockey fixture or how the dreadedmaths test went. There's a difference between not liking someone and respecting them. You'll always have kids that are challenging but once you know who they are you can plan accordingly to integrate them into lessons more.
The bane of my life to start with. All I seemed to do was plan lessons. But planning pays off. The lessons where you skimped on the planning show and the lessons you put the time into the planning stage will be your best. If possible, plan with other teachers so you can bounce ideas off them and ask for advice - they've all been in your shoes before and will have tricks of the trade they can pass on to you.
4. Mentor meetings
Make sure you have them. I've been lucky enough to have two excellent and inspiring mentors and meeting with them once a week has improved my teaching no end. Pick their brains, ask for help, watch them teach, plan a lesson with them, plan a lesson for them - that last one is a really good activity to do; did the lesson turn out as you envisioned? If your meetings aren't happening, firstly, shame on your mentor, and secondly, put your foot down and make them happen. If that doesn't work ask your university tutor to arrange for a replacement.
Putting your foot down with 30 rowdy teenagers can be pretty tricky if they don't know or respect you. If their usual teacher has a routine use it, if not, start one for yourself. Learn their names - full disclosure, I'm terrible with names - and once they know they're on your radar they'll play ball (hopefully). Try and avoid handing out detentions willy-nilly, but if you feel you’ve got an issue make sure you follow through. Just like Jaws, the kids will smell blood if you fail to deliver on a threat.
6. Have fun!
This one is probably the most important tip. Make sure you're not working 24/7 or you'll burn out. If you're not enjoying yourself then the school week is awfully, awfully long.
Before you start your course
Find out more about preparing for teacher training