Big Cardigan tucked down

1. Try on the cardy and mark where your shoulders really are in the sweater (not the seams of the sweater's shoulders but your actual shoulders). Also mark where you boobs are — say in three lines to of boob, middle of boob and just under the boob. 
2. Do the math to figure out how much of the sweater you are gonna have to tuck up to get the shoulder seam to come to the place your shoulder is. Figure out how many tucks you want and mark them out in chalk with a ruler. 
3. Pin and sew. Keep in mind you can always take more tucks but ripping them out is gonna be a way bigger pain than it will be worth. 
4. if it is still baggy on the bottom use pins and pull a bit from the back and a bit from the front to find out how much you will have to tuck ... you want to place your front and back tucks about the same place you would find princess seams or darts. Do the math, mark it out and pin it up... try it on before you sew.. and as you tuck.. do one set of tucks, try it on, and keep tucking until you get the fit you want. 
5. Next, if the sleeves are to big you can tuck them too. With the sweater on mark how much you are gonna have to tuck up as well as were on the sleeve you want the tucks to show. Do the math, mark it out and sew those tucks on up... I am trying to mimic a fairly deep cuff on mine.