Plan around your shoes first
If you want to maximize space and bring as much as you can without checking a bag, adhere to a clothing hierarchy. Not all items are created equal, and at the bottom of that totem pole (and the bottom of your bag) should be your shoes.
“Limit the amount of shoes you bring. These take up the most space in your suitcase,” says one American Airlines flight attendant. A good way to make use of your shoe space is to bring flip-flops or flats, which take up zero space, a pair of boots/sneakers/walking shoes (which you can wear on the plane), and one pair of dress shoes.
“Then,” the flight attendant says, “fold all jeans and pants as you normally would and roll them up, placing them on top of the shoes next to each other. Then do the same for shirts. Lastly, all underwear and socks go on the top or in empty crevices.”
Another American flight attendant also adheres to the rolling rule, and suggests investing in a small travel iron, should you value wrinkle-free clothing.