Measure around the mid-section of your bicep. Use your weaker (less used) arm. Let your arms hang naturally, don't flex.
You will need some help with this one. Relax shoulders. Measure between shoulder bones with a slight arc. Do not go all the way to the outside of the shoulder muscles, rather to where the bone stops. Tip: Wear a shirt that fits you well, and measure between shoulder seams.
Run measuring tape around the widest part of your chest. This is usually directly under the arms. Keep the tape as horizontal as possible. Relax your chest in a natural position.
Run the tape measure around the widest part of your waist. This would usually be around the love handles. Don't suck in your stomach. Tape should be snug but not tight.
Look in a mirror and identify the widest part of your buttocks. Then place the tape measure at this location and measure around the circumference of your hips and buttocks.
Measure the circumference of the widest part of your forearm.
Get help for this one because it is hard to do yourself. Place your hand at your waist (your elbow should be bent at a 90-degree angle). Then start at your shoulder seam and measure to your shoulder, down your arm to the elbow, and then on to the wrist.