Fold the sports coat in half such that the two shoulders are side by side.
Be sure to dimple the collar in the center with a light tap so that it does not buckle outward.
Slide your hands inside lapels and smooth out any creases in jacket lining.
Slide one arm behind each lapel and move hand until it is underneath the shoulder and finger tips are touching the far inside edge.
Turn one hand so it is perpendicular to the other (like making a time-out sign) and then continue to turn that hand until the front of it is essentially facing the palm of your other hand.
Slide that hand inside the shoulder of the other side and fold the jacket inside out so that the two lapels are facing each other and one shoulder is tucked inside the other.
The jacket is now ready to be placed into your suitcase. If you need to fold it lengthwise, that is fine. As soon as you can unpack, hang the jacket up. It should be relatively wrinkle-free.