You can reduce clothing wrinkles by reducing the friction caused by shifting items. Wrap each hanging item in an individual dry cleaning bag, then roll the item while it's in the plastic bag.
Fold jeans and pants in half lengthwise to prepare them for rolling. Begin at the cuff and tightly roll the jeans toward the waist. Secure the pants with a rubber band, if you like, in order to keep them rolled up.
Spread T-shirts face down on your bed or table. Fold the arms toward the back of the shirt, creating a rectangle shape. Fold the shirt in half lengthwise and smooth it out. Begin at the bottom of the shirt, and tightly roll it up toward the top. A rubber band around your T-shirts will keep them rolled up.
Roll up your socks and put them inside of the shoes you pack. Roll up all of your undergarments, as well.
Pack your heavy and folded items into your travel bag. Place all rolled clothes in the space around those items. Tuck your shoes into remaining openings. Pack your rolled undergarments into the small zipper sections of your suitcase.