A messily packed carry-on can trigger a hand search at the checkpoint because your belongings may pair up in strange ways under the X-ray. Pack in layers, with the heaviest items on the bottom, followed by clothing, electronics and toiletries on top.
Follow the 3-1-1 rule for liquids. Bottles no more than 3.4 oz. by volume, packed in a 1 quart, clear plastic zip-top bag, and no more than one bag per passenger. Liquid medications and baby formula may be in larger quantities, but you must declare them and have them inspected separately.
Your laptop may remain in a "checkpoint-friendly" case. Such a case is without snaps or zippers and lies flat on the conveyor, providing an unobstructed X-ray of the laptop only. Don't put cables, extra batteries or papers in the bag or in any outside pockets. Even then, you may be asked to show the laptop. Small electronic devices like iPods and cell phones can stay in your carry-on.
Carry on undeveloped film because the stronger X-rays screening checked baggage could ruin it. If it is faster than 800-speed, ask for a hand inspection. Pack spare batteries in their original packaging or cover the contacts with tape so they don't touch metal and spark. If you pack battery-powered device without a case, tape the on/off switch in the off position.
Lock your bags, but only with TSA-approved locks that can be opened with a master key. Otherwise, your locks will be cut off. You may also use plastic loops typically used for bundling computer cables because they are easily cut off. Pack some extras for your return trip. Be sure not to wrap any gifts that you bring.
Pack any food that doesn't fit the 3-1-1 rule, even if it is semi-liquid like peanut butter or a dip. Put it in a sealed plastic bag in case it leaks.
Group clothing in large, clear plastic bags so the TSA can quickly see what is in your luggage during a hand search. The old space-maximizing trick of stuffing small items in places like shoes can backfire and get your bag ransacked if the TSA thinks you are hiding something, so think transparency.
