the photos below should be used as indications for where each measurement should be taken.
please make sure you are measuring from the correct side of the measuring tape, and give all measurements in inches. 
having a friend help you is always a good idea for accuracy.

bust: should be measured around the
widest part of the bust
(usually right through the nips)

waist: measure at the smallest
part of the waist
remember to leave space to breathe.

hips: measure around the widest part
of your hips through
the fullest part of your bum