Since there truly is no modern size standard, it's very important to know your measurements when ordering clothing by mail. It is easiest to take your measurements with a cloth tape measure, but if you don't have one you can use a piece of string. Simply mark the string as you measure and then measure the string with a ruler.
Do not take your measurements while wearing bulky clothes. To get the most accurate measurements it is best to measure while wearing only your normal undergarments. If someone is helping you and you are uncomforable with this, you can wear a thin tank top, etc...
Never pull the tape too tight to make a measurement work... be completely honest with yourself or the result will be a garment that doesn't fit properly.
Measuring Bust Size: Measure at the fullest part of the bust (see diagram at bottom of page). Please note, this is not the same as your bra size. If you wear a 34C bra, this does not mean that you have a 34" bust.
Measuring Waist Size: Measure around your natural waist line (see diagram at bottom of page). Your natural waistline is the smallest point. If there is no clearly defined "smallest point" measure at the navel line. Don't suck it in or pull the tape too tight, though, or you may end up with a dress that is too snug. Alternatively, don't let the tape hang TOO loose or measure over an exisiting waistband or you will end up with something too large.
Measuring Shoulder to Waist: Measure from the front shoulder (where the normal shoulder seam would fall), over your bust to the waistline.
Measuring Hips: Measure around the fullest part of your hips. If the tape can easily be moved up and down, it's around the fullest part (this is usually about 7 to 8 inches below the natural waistline).