1. Don't think it is going to be easy - it won't. Be ready to get your lessons ready at night, have some nightmares at night at the eve of your lesson. But that's not so strange for us, teachers.
2. Be careful with the equipment - everything can fail so have some additional material in a paper variant.
3. Be friendly - remember that other participants are not your rivals, they are actually in the same position as you are so try to help if you are asked to.
4. Calm down - more nervous you are, more nervous the kids will be. They feel everything. If they are afraid - they can't work well and you need their help.
5. Smile - always smile and it should be natural. Even if something is not right, at least you won't show it to everybody.