i think the percentages vary from person to person but i have always gone for 30% fat, 30% protein and 40% carbs.

if you have the time, Jillian Michaels has an interesting way of establishing what your percentages should be based on what she calls oxidizing. you are either a balanced oxidizer (even spread), fast oxidizer (more protein, less carbs) or a slow oxidizer (less protein, more carbs). you can take a quiz that is in her book Winning by Losing (which is a great resource to have!) or taking a niacin or vitamin C test to determine which oxidizer you would be.