Fire eating is pretty easy - you just breathe out whilst holding the torch in your teeth with your head titlted back. Fire breathing is horrible though. Almost all of the fuels that people use to do it mess you up in some way.
A friend of mine managed to burn his hand. The sambuca had been flaming for a while so the glass was hot and he tried to put the flame out by placing his hand over the drink. Produced a very amusing perfectly circular burn on the palm of his hand