Start the car and let it build up vacuum. Turn it off, press the brake pedal down with the car off. Start the car and the pedal should depress if the booster is good. if the booster is bad there will be no change. TIA Pete

Pete,
Yeah,thats basically it.If you have a good check valve it should take about 3 or 4 depressions of the brake pedal to use all the stored vacumm in the booster.The pedal should now be high and hard,hold it there as you start the motor.If the booster is good the pedal will drop noticeably.
If the booster is shot OR you have a lack of vacumm the pedal will stay basically the same height.