The key to figure flattering clothing is knowing your measurements. It's always easier done with a friend. Most tailors offer this service for free.
BUST: The bust should be measured at the fullest point.
WAIST: Stand up straight and measure at the smallest part of your waist.
HIPS: Measure at the fullest part of the hips.
INSEAM: Start with a pair of pants that fit you well. Measure from the crotch down to the bottom of the leg.