First, shoot for 1 g/lb bodyweight of protein. Multiply that by 4 cal/gram to get the amount of calories from that protein. So, say you weigh 180:
180 g/protein X 4 cal/gram = 720 Calories from protein
Split the rest between carbs and fat, with at least 50 g of carbs occurring post-workout to replenish glycogen.
So, say you've picked a reasonable caloric deficit. For our 180 lb. guy, this might be 2000 cal/day.
720 calories of that is protein, so 35% of your calories from protein. That leaves 65% of 2000 calories to split between carbs and fat. I suggest you go more carb-heavy for the sake of glycogen. So let's go 40% carbs and 25% fat.
That would give you 800 calories from carbs, or 200 g of carbs (at 4 cal/gram), and 480 calories from fat, or about 55 g of fat (at 9 cal/gram).
So there's a reasonable 35/40/25 ratio.
-casualbb