I've had a dig through the library in the knitting room and the resource of choice is going to be the eternally authoritative Readers Digest Complete Guide to Needlework (1981). It has only one chapter on knitting but that chapter is full of the most clear and sensible technical advice you could wish for. I am instructed that to plan the armhole, we'll need the following measurements:
- Shoulder width: distance across the back between the armholes;
- Chest: underarm measurement across half the garment;
- Shoulder length: "standard for your garment size";
- Armhole depth: "standard for your garment size".
To plan the sleeve we'll need these measurements:
- Underarm length;
Excuse me while I go away and work out what all those measurements are.