One of the things that can make or break a sweater is your armhole depth. If it’s too tight, your sweater will bunch under the arm (not to mention be very uncomfortable), if it’s too loose your sweater can look sloppy.
On my Ravelry group we run video sweater KALs several times a year. The KALs are filled with video tutorials and how tos (exclusive to the KAL participants) and there’s always information on picking the right size.
You can find out more about my video sweater classes here
Choosing the right size is the most vital step to a happy sweater, and a very important element of that is understanding . . .