Lay suit facedown on a flat surface.
Fold left shoulder back.
Turn right shoulder inside out, then tuck left shoulder into the right.
Fold in half lengthwise and then fold horizontally.
Place folded jacket in the middle of outstretched pants.
Fold pant bottoms over jacket and then fold the top of the pants over the jacket.
Pack your suit last on top of everything else in your carry-on bag.