There’s an art to packing a carry-on bag. Wise travelers must balance the requirements of airlines and airport security, make sure important items are easily accessible, and remember all the little things that will keep them comfortable in flight. In the spirit of 10 Things Not to Do When Checking a Bag, we’ve gathered seven common carry-on bag mistakes. Steer clear of these, and you’ll save money, have a better flight, and avoid running afoul of airport security.