I got a couple of awesome sweaters for Christmas, but they’re a little big. How can I shrink them, but not to cartoon-size, and also without distorting them?
Well, first of all, I’ll assume they can’t be exchanged, so what are they made of?
Cotton sweaters probably won’t shrink, having been pre-shrunk before knitting. But washing and drying on hot will shink them if it’s at all possible.
With cotton/ramie or silk blends that say ‘lie flat to dry’, it’s not shrinking you have to worry about so much as stretching.
Wool and angora can be ‘shocked’ into shrinking by washing and drying on hot, but I see a lot of sweaters like this in thrift stores and it’s not pretty.
What you need to do is ‘controlled shrinkage’:
http://www.mkeonline.com/story.asp?id=368944
The important thing is to do it slowly and gradually, or you’ll wind up with felt. They don’t call 'em “boiled wool” jackets for nothing.
Ooh, bad idea. Shrinking happens when the individual fibers contract. So you’ll have a sweater made with fibers that are no longer long, thin, and supple; but are now short, fat, and stiff.
Exchange them, or wear them loose. Or eat a pie. Don’t shock-shrink them.
Trust me - Let my mother-in-law wash them. One time when we went to visit her, she insisted on washing all our clothes. Let us just say, the trip became an excuse for buying new clothes.
What’s the material? If they’re made from acrylic or acrylic blends, they will not shrink.
"How do I shrink clothing?"
Gain weight. It worked for me. 
Sweater 1: “Merino Wool”
2 and 3: Acrylic