A popular home method you can try is to use cabbage leaves. One of my friends placed cool cabbage leaves in her bra and it worked for her. She would replace the leaves at the end of the day or when they have wilted, whichever comes first. Apparently, cabbage leaves have a property that naturally dries up your milk.
I also read that drinking sage tea will dry up milk. Sage contains a natural estrogen that supposedly dries up milk supply.