One day is definitely not enough. Even 2 days are just barely good.
I don't know any very useful trick but if you do some study before you go, knowing which stores you are going, finding out their locations, printing out all coupons you probably will need, and planning your route according to your desire, you will save some time for sure.
Also, don't even think visiting most of the stores. Just pick about 10 to 20 stores into your list. If you really want to buy some clothes, you will need 0.5 to 1.5 hours in one store because you need try them on.