You may have already experienced it when travelling. You scrupulously ironed, folded and packed your shirts into your suitcase before leaving, and everything was creased when you arrived!
My advice: protect them by using a cardboard (rigid enough), put the shirt into it then place it in the middle of the suitcase stucked between the shoes (from the bottom) and the jackets for example (on the top). I usually put two shirts into the same box in a 69 position. Once arrived and taken the shirts out of the case, they are in a totally wearable condition!
One other more elaborated solution: some luggage brands propose specific boxes allowing a better organisation of your suitcase by seperating the clothes in different comptarments. I have tried one from Tumi which looks interesting, but in practise the shirts did move anyway. My guess is: a lower size would be more suitable. Tumi calls it “packing cube” (sold between €30 and €50). What about you, any tip for this?