Height
From the floor to the top of your head, best measured against a wall.
Chest
Measure horizontally under the armpits around the fullest part of your chest and shoulder blades.
Waist
Measure the waist circumference at the smallest part of your waist.
Inside leg
Measure from your ankle bone to your groin.
In between sizes
MB (Medium Broad) has the length of a Medium and the width of a Large suit. LT (Large Tall) has the width of a Large and the height of an Extra Large suit.