Just work out your daily needs and then take off 1000 calories worth in fats and carbs and your fat% will take care of itself. If you go too low you will lose too much lean body mass. I have been on this for 6 weeks and have lost about 6 pounds. I also run and lift weights though so I play with the carbs a little more due to its Anaerobic nature and it being fuelled differently than cardio exercise.
Anyway, on this plan you will lose about 100g a day.
If you can jog then do that, it will burn more calories fastert than a bike (not as much fun though) it also mixes things up and you can increase your bone density from it.
If you can find a place to lift do that too, remember the bigger your LBM the more calories you are burning all the time.
While its supposidly impossible to build muscle while on a negative calorie diet, you will find that you will be gaining good weight dispite the low calorie intake, just make sure you are eating primarily low glycemic index carbs and a good low animal fat protein.