Here's a three step way to make sure you take the most accurate measurements:
# Take 2-3 measurements of each.
# If possible, have a friend help you, especially with bust and sleeve length.
# Use the average of the 3 measurements when deciding on your size.
* Hips
** Measurement taken from 7"-8" from waist.
** Circle the fullest part of your hips.
* Sleeve
** Measured from center of back.
** Bend arm to 90 degree angle with one hand on hip.
** Take measuring tap down elbow to the wrist.
* Bust
** With arms at sides measure the wides part of bust.
* Waist
** Do not measure over clothes.
** Measure where you wan to wear your pants (i.e. the natural waist or lower)
** Keep the tape measure comfortably loose.
* Inseam
** Use a pair of pants that fir well and measure from crotch to bottom hem of pants.
** Add 1/2" to measurement for cotton pants that have not been prewashed.