The sleeves
When a sleeve is of the right length, the cuff lays at the base of the thumb.
The sleeve has to be long enough to peek out of the jacket sleeve about one centimeter when the arm is alongside the body.Otherwise the cuff will disappear in the jacket when you sit down or when you raise your arm.

The cuffs
The cuffs must adhere but should not be too tight on the wrist.
You get the right measure when you move your arms in any direction and the cuffs move justy a few millimeters. A trick could be to increase the size of the wrist by one-third.

Any cotton shirt will shrink at least for the four or five washings, so when you buy it, it should be loose on your neck and long on your arms, so later it will fit you perfectly.

The collar
When the collar is buttoned, has to leave space to put your little finger in. The collar circumference has to be comfortable to allow your head to turn easily but holding the points down on the front, even when you turn your chest.
Besides the height of the collar has to allow it to show of 1 cm and half from the neck of the jacket, on the nape.