How do you set up a diet for fat loss?

A 500 Calorie per day deficit will give you 1lb of weight loss per week mathematically (assuming your metabolism is perfectly constant every day). A 1000 Calorie daily deficit will give you a 2lb weekly weight loss (again, assuming perfectly constant metabolism).

You can assume that you burn somewhere between 200-800 Calories while training. If you're a freak that squats 600lbs for sets of 10 all day long, it might be higher, but to keep it simple, let's say you average 500 calories per day training.

So, let's do some math:
Training day BMR: 3800 Calories
Off day BMR: 3300 Calories

Assuming you train 5x a week that gives us a weekly Calorie total of 25,600 Calories. To drop 2lb of fat per week we need 18,600 Calories.

But how can you make sure the lost Calories come from FAT and not MUSCLE? That is where proper macronutrient partitioning with a professional diet plan comes into play.