Definitely don't keep something that's going to wrinkle toward the bottom. Always keep those near the top of the suitcase. Make sure your shoes or toiletry bag isn't crunching it.
Rolling really does maximize the space in a suitcase. Also, if you’re packing boots or anything like that, there is open space in the boot. You could put socks in...
Save your pieces that are most likely to wrinkle for last when you're packing. Then, lay these items on top of your other clothes so they're less likely to crease...