BUST
Unless you intend to wear the garment without a bra, we recommend measuring the bust with a bra on.

To measure your bust, lift your arms and measure around the back, under the arms to the part which goes across both of your nipples.

WAIST
Your waistline is about halfway-ish between the bottom of your ribs and your hips, above your belly button, it's most likely the narrowest point.

To find your natural waist, stand up straight and bend side to side, finding where your body creases. At this point, wrap the measuring tape straight across. For many, it is the smallest point, but it may not be.

Relax your tummy while measuring. Ensure the tape measure is neither too tight or too loose.

HIPS
Your hip measurement is across your booty at your widest point. For an accurate measurement, measure without clothes on (just panties) and make sure to stand with your feet together.

Place the end of the tape measure on one of your hips. Pass this around your body, over your bum and your second hip, and then back to the starting point.

You need to ensure that the tape remains level all the way around and is parallel to the floor. Measuring in front of a mirror can be useful.