1) Line the bottom with a plastic trash bag. After you've packed add another one on top. This helps fend off wrinkles and will keep it dry if it's off-loaded from the plane in the rain.
2) Stash footwear and heavy stuff along the wheel base. Fill shoes with socks or bulky bangle bracelets, then put them in individual bags or shower caps, with the soles facing the sides of the suitcase. Splitting up the pairs saves space. Rest other heavy items like a hair dryer or a toiletry kit next to or on top of shoes. Placing these things near the wheels stabilizes the bag's center of gravity so it won't topple over when upright.
3) Lay the foundation next by tightly packing rolled clothing.
4) Build the second layer by layering folded dresses, pants, and skirts on top of the rolled clothes. Alternate the sides that the waistbands are on so the stack is balanced.
5) Finish with the top level by layering crushable items such as a voluminous dress or molded bras. Stack bras flat so they spoon each other and stuff the cups with socks.
6) Wrap belts around the interior frame of the bag.
7) Stock essentials, loose toiletries and chunky costume jewelry in the lid compartments. Store delicate earrings in pill cases and string dainty bracelets and necklaces through drinking straws, taping the clasps to one end. Then secure the straws, in a plastic bag.
8) Tuck leftovers like swimsuits, hosiery, underwear, scarves - into corners and any remaining nooks.
9) Pack along a few large zippered plastic bags so you can store dirty laundry in. Press out the air and you tightly roll each bag like a vacuum pack. Lay the compressed bags flat in a side pocket.
10) Cradle fragile souvenirs in the bulkiest sweaters and arrange them in the center of the bag, where there is the least movement. For extra protection, store messy liquids - like that bottle of EVOO from Tuscany - in a reusable inflatable plastic bag designed for this job. (Try the VinniBag; $28, vinnibag.com).
If you aren't using a hard suitcase but rather a soft sided bag like a duffel or a weekender, place flat shoes along the bottom, with the soles pressed against either side. Add rolled clothes, packing them tightly to prevent shifting in transit which causes the most wrinkling. From there follow the accessories tip listed above with these exceptions: lay heels and boots flat on the top of the bag, then add the toiletry kit.