Now to eat it:
1. lean you head back, so that your face is parallel to the ground. You want to give the fire as wide a target as you can.
2. that entails opening your mouth as wide as you can also.
3. smile as big as you can. Your lips do not have the wet protective coating that the tongue or insdides of your mouth do. The fire will burn your lips, so keep them away!
4. exhale slightly. Not so hard, or you'll extinguish the flame (it's really that easy to put out.) What you do not want to do is inhale. Inhaling fire can be a problem if you do it. Scratch that. Inhaling fire will be a problem if you do it. Exhaling slightly keeps the fire away from you and going out of your mouth where it should.
5. hold the torch vertically over your head and lower the flame into your mouth. If the fire is too high it may be difficult to hold on to the torch, so you might have to wait for it to die down a little bit.
A lot of the trouble is gauging how close the torch is to your mouth. It's hard to see, and I actually found it's easier if I just didn't look at it. I line up the torch above my mouth and them when I lower it I stop trying to watch it as it leaves my view, and I judge by the heat how close it is, and if I'm too close to my tongue, teeth, etc. You'll be able to feel it, and you'll know when it's too close, in plenty of time to avoid getting burned. That part just takes doing it a few times to get the feel. After that you can just pop it in no problem.
When the flame is in there remember not to inhale (you should be exhaling slightly.
When you want to "eat it" (put it out in your mouth) you can actually do it by exhaling harder than you currently are. That's enough to do the trick. But it doesn;t look as cool. If you have the flame in enough, so that the majority of the wick is in your mouth, you can close your teeth quickly around the torch and that will put it out. It closes the air off enough. Just to be safe, when I close my teeth on the torch I also exhale harder just to make sure it goes out. But by closing your mouth around it it gives it the "eating" look.
Obviously, next, take the torch out of your mouth. It will be smoking, and you don;t want to inhale that.
That's how you eat fire!
If you're really nervous about it, remember that the fire is so easily put out that if you really need to get it out you'll do it instinctively without any problem. Just donit inhale it!