One of the ways I save space in my suitcase is with bags that flatten your clothes so they take up less space.
The bags I use are sold at Target and other discount stores; you put your folded clothes in the bag, close it up, then roll the bag to push out the air (there is an opening at the bottom of the bag to let the air out).
These bags let me zip my suitcase closed more easily. I try not to take MORE stuff, because the bag starts getting too heavy! But it's also nice to keep your dirty laundry separate from the clean stuff on the way home, too.