I do it the BFL way. On a level of 1-10, it's a minute of 5, a minute of 6, then 7,8, and 9. This is a total of 5 minutes. Do this for 4 - 5 minute sessions, each time starting back over on level 5. The only difference is that on the 4th set I want to hit "10" for intensity for the last minute. This means that last second is the last second I can take of it. If I do it like that, I've hit my 10! I do this for 20 minutes, then I cool down 5-10 minutes. BFL calls for 20 minutes a day, 3x a week, but most people I hear from do it more often.
Try doing a search in the Exercise forum. I know there is a thread on it somewhere, and I believe that is the place.
We're fat chicks, not doctors. Please see your physician before taking advice found on the internet.