Open up the duffle and fold down the open ends on the outside of the bag to ensure the zipper does not get caught on any clothes, pulling on them and causing a snag.
Fold your clothing in as flat a way as possible. If you want to get the clothing extremely flat, use a vacuum sealer with clothing bags. This reduces clothing items to the smallest fit possible and wraps them in plastic, ensuring protection against any water or fluid spills. In addition, roll items such as T-shirts into long tubes and stuff them into the gaps on the side of the duffle.
Pack the clothing items you need least in the very bottom of the duffle. For example, if you are going casual yet have one formal outfit, pack the formal clothing at the bottom because you won't need it while on the go.
Stack the clothing up in the duffle like stacking chips in a can. When you feel the stack getting sideways or shifting, pick up the top ends of the duffle, shake up and down a few times, then hit the bottom on the floor to settle the clothing.
Close the bag using its mechanisms. Some have latches, while others use zippers. If traveling where theft or security is a risk, lock the closures with a small padlock. If flying in the USA, make sure the small padlock is TSA approved (see Resources for TSA information on approved luggage locks).
