I have taken this from http://www.thechicfashionista.com/body-measurements.html and edited it for myself. Please follow these directions when you order something from my Etsy store at http://www.etsy.com/shop/stinigurl. Thanks!
Measuring Your Body Step-by-Step
You might want to print out this page so that you can write down your measurements after each step:
Shoulder to shoulder (1): Measure in a straight line from the outer edge from one shoulder to the other.
Bust (2): Under your arms, around the fullest part of your chest (usually on your nipple area). Wrap the tape around your back and forward to the fullest part of your bust.
Underbust (not pictured): Measurement taken under your bust above your ribcage, where the bottom band of your bra sits.
Natural waist (3): Around the narrowest part of your torso. Usually 1-2″ above your belly button. NOT NECESSARILY WHERE YOU WEAR YOUR PANTS!
This is one of the areas we tend to pull in when it is exposed. That’s natural, but try to avoid holding your breath. You don’t want your new garment to fit too tight!
Hips (5): Measure around the widest part of your hips (usually the area where your hip bones are located). This should be done with your feet close together. Measure around the fullest part of you rear!
Rise (4): Measure from your natural waist down to your crotch. Hold the tape a little loose, gently pull it through the legs (from your crotch, between your legs) and up to the same level as your natural waist.
Inseam (6): From crotch to the inside of your ankle. Start from the ankle and up. This is best done with a partner. PS: This is how you find your best pants length (petite, average or tall)