Have your students practice their "Elevator Pitch". It's a short speech/conversation about the team and what FIRST means to you.
Search Chief Delphi for examples like this
one.
Jenny pointed you to some great resources. Check them out. There is a lot of material in the Nemo site.
Have your students practice engaging someone role playing the judge. I see so many teams that are not aware that a judge is there. Greet them, introduce yourself, shake their hands and engage them in a dialogue. You have a built in advantage that you are from another country. Use it.
Good luck, Have fun