Shoulder Width
This is an important measurement. Start across the top of your shoulders, measure from your left shoulder to your right shoulder as shown in the image. For any anatomy-inclined users, the stopping point is where your shoulder bone turns into your rotator cuff, lifting your arm a few times should make this obvious. Usually 18-22 inches
Sleeves
Be sure to let your arm hang in a relaxed manner. Measure from the end of the shoulder to just above the base of your thumb. You may also measure to the end of your sleeve of your favourite shirt. Usually 23-26 inches
Front Width
Start where your pastoral muscle meets your armpit and come in 3/4 of an inch toward the centre of your chest. Stand naturally, stretch the measuring tape across your chest and record your measurement. Usually 14-18 inches
Back Width
Find where your shoulder blade meets your underarm, approximately 3/4 of an inch back from your shirt seam. Stand naturally and stretch the tape across. Measure at the same level on the body as you did in the previous measurement. Usually 14-18 inches
Biceps
Measure around the fullest part of your bicep, it is as easy as it sounds. Most bicep circumferences should be the same for each arm. Usually 12-15 inches