How to measure correctly
The best way to measure, is to use a tailors measuring tape. If you don´t have any of these at home, you can simply use a longer piece of cord and a ruler. (Put the cord around your bust, waist or hips and mark the beginning and the end with your fingers. Then measure the marked length with a ruler.) You can take the measurements by yourself while looking into the mirror, or ask a friend to help you.
Take a tape and measure around the widest part of your chest. (without bra, unless you are wearing it during dancing as well)
Position the measuring tape around the narrowest part of your waist.
Measure horizontally around the fullest part of your hips and buttocks. The best way to find the fullest part, is to look at you in profile.