This is coming from Pro Bodybuilder Tom Prince on another board...I agree that this is the best way to do cardio to cut fat..
I start doing cardio at 16 weeks out from the day of the contest. I START with 20 minutes per day, 6 days per week. Each week, I add 5 minutes to the amount of cardio I do each day. So, week #2, I do 25 minutes per day. Week #3, I do 30 minutes per day. And so on. I keep adding 5 minutes every week until I get to 80 minutes. I also split cardio into 2 sessions/ day, when it gets to 40 minutes a day. 20 in the a.m., 20 in the p.m. Cardio done AFTER workout.