it's all about minimizing the volume of the items and making the various shapes fit in the available space of the suitcase.

heavy things go in the bottom and strapped down on their own and the clothes all "float" inside the case, albeit packed tightly so they don't all slide around.

i roll underwear, socks, shorts, jeans, tshirts and polo shirts. i fold button-down shirts, dress pants and suits. stuff things into the shoes (usually socks).

shifting contributes to wrinkles so if you have extra room; get a smaller suitcase or pack more stuff.

one thing that can help is to use the plastic hanger wraps the dry-cleaner uses to wrap clean clothes. They're slippy and you can layer items with them to keep bunching to a minimum. Suits can tolerate wrinkling better because you can steam them in the lav ~ hot shower and close the door.