Place tape around neck at the level the shirt’s collar would be
buttoned. Place two fingers between the neck and the tape. Make
sure the tape is snug, but moves freely.

When measuring the sleeve length, make sure
you start the tape just below the neck, centered
with the spine. Make sure the tape measure
goes over the top of the gentleman’s shoulder. 
Take the tape down the arm to the point of his
elbow, and then measure an inch and a half past
the wrist bone. It is always better to measure
long versus short because a sleeve that is too
short will likely be unacceptable.