A - Chest
Put one end of the tape measure on the fullest part of the chest and bring the tape around the back (under the armpits, over the shoulder blades) to where you started.
B - Waist
Place the tape on the narrowest part of the waist and measure around.
C - Hips
Put the beginning of the tape measure on one hip and bring the tape across the fullest part of the hips back to where you started measuring.