The best thing to ingest before attempting this is charcoal tablets bought at a pharmacy, they prevent the fuel from being absorbed into your system if you accidentally swallow any. Before you put anything in your mouth have the light torch and a wet towel close by. (Use the wet towel to wipe your mouth off after each time so no excess kerosene builds up on your face and ignites, that would be bad) The most important thing to remember the first time is to start small and work your way up. Its hard (not impossible) to burn yourself with just a quarter of a tablespoon of kerosene in your mouth, so make sure you start off with a small amount.
When you feel you are ready take a small sip of the kerosene, close your lips, and hold it in your mouth. Pick up the torch in one hand and the wet towel in the other. Hold the torch slightly closer then arm fully extended. (Make sure you are facing the direction the wind is blowing) Take a big breath in through your nose and with your head tilted slightly upward spray the kerosene out over the flame. When there is no kerosene left in your mouth quickly wipe around your mouth with the wet towel.
Now for an explanation for some of this. The reason you want to hold the torch far away from your face is so you can avoid a blowback. A blowback is when the flame travels along the stream reaching your mouth and burning your face. Blowbacks can be avoided in three easy ways
1. Never overfill your mouth with kerosene (If your lungs run out of capacity before your mouth is empty the flame will travel back into your face, if you feel this is about to happen the best thing to do is to quickly open your lips and spit out the remaining liquid, and bring the wet towel infront of your face to protect from any flames)
2. Always keep the torch a safe (at least 2 feet) distance from your face. (As you can see in the photos the flame traveled towards my mouth from the torch, but I ran out of kerosene before it hit my face)
3. Always spray as fast as possible, this will make it harder for the flame to reach your face.
Some basic rules:
1. Never play dragon and set anyone on fire
2. Never do it in an area with anything flammable
3. Make sure there is nothing ahead of you for at least 25 feet and nothing above you for 20
4. Never do this indoors
5. Always have a fire extinguisher, bucket of water, and wet towel
6. Never do this under the influence of alchol or drugs, HOWEVER you can do this in the PRESENCE OF THOSE who are under their influence (Its a very easy way to entertain drunk people, but then again what isnt)
Again heres the link to the videos of me breathing fire http://video.google.com/videoplay?docid=-2276917600442809328