Eat Or Not to Eat Before a Workout?

Hello friends,
Is it better to eat 1/2 hour before a workout? An hour before a workout? Don't eat? Yes, eat. Eat what? When? As Personal Trainers, we get these questions all the time. These question are always in my mind. So can any body help me to solve these problem. Your suggsation will be very helpful to me.
Thanks.