Bust: Measure around the back, under the arms, and across the bust at the fullest part. It is best to do this with a bra on (not a pushup bra). 

Underbust: Measure directly under the bust, around the ribcage.

Natural waist: Measure around the smallest part of the waist just above the belly button.

High Hip: Measure around the protruding points of your hip bones, about 3" below your natural waist.

Tip: If you do not have a soft measuring tape, use a piece of string and a ruler.