Hey Christiaan,
just fold your tshirt half way and start rolling it tightly. Do the same with underwear, pants (maybe not your suite, but jeans will be fine) and the like. It saves space, and they don't wrinkle.
It really works, but I usually only do it when packing my backpack - my suitcase has little straps to fasten folded things down with and I never pack it too tight either.
Nic