Do you know how I can stay healthy during a trip?

This is by no means my first flight, but this is the first time that it is absolutely essential for me to be healthy during a trip because I am traveling for a competition and I have to give several verbal presentations. I was wondering how I can stay healthy because if I get sick, I would be let down my whole team. I know the obvious like wash my hands, drink lots of water, etc., but is there anything else I should do? Anything I should or shouldn’t eat or drink?