It is simple to measure yourself..

To measure Across your Bust: Measure across the largest area of your bust

To measure under your bust: Measure underneath your bust

To measure your waist: measure across the smallest part of your waist

To measure your bum: Measure across the largest area of your Bum

Measure from your waist down to where you would like your dress to end without bending down

For One pieces or Bodys measure your torso from shoulders down.