Head - For greatest accuracy, have someone else measure around the largest part of the head, just above the eyebrows.
Neck - Measure around the base of the neck allowing for a comfortable fit, or measure a shirt collar that fits you well. To measure a shirt, lay collar flat and measure from button to button hole at the far end.
Sleeve - With slightly bent elbow, measure from the center back of the neck, over the point of shoulder and down the outer side of the arm to wrist bone.
Chest - (Men) With arms relaxed at sides, measure around the largest part of the chest and around shoulder blades.  (Women)  With arms relaxed at sides, measure at the fullest point of the bust and around shoulder blades.
Waist - Measure around waist at narrowest point or at the height you normally wear your pants keeping one finger between tape and body. For belts, add 2" to your waist size.
Hands/Gloves - On adult gloves, your hand circumference in inches equals glove size.  Measure around a flat hand at the knuckles, do not include thumb. 
Inseam - Wear shoes and have someone measure from base of crotch down inside of leg to ankle bone or desired pant length.