How to measure your bust/chest: WIth arms relaxed on both sides, measure under the arms around the fullest part of your bust/chest.
How to measure your waist: WIth heels slightly apart, measure around the narrowest part of the waist.
How to measure your hip: WIth the heels slightly apart, measure the fullest part of the hip.

Keep the measuring tape parallel to the floor for the best result.