We've all been there. You're packing to return home from a trip, but when everything's in the suitcase, you discover you bought just a tad too much stuff. It won't all fit.
The airlines want you to check a second bag so they can rake in more fees. But as long as you only have a few things spilling over, there's a smarter way.
Go online. See what shops are in the terminal you're going to be leaving from. Nearly all major international airports list their amenities on their websites.
Most of the shops will be chain stores (airports rarely give mom-and-pops a chance anymore). Go get a shopping bag from the nearest one—buy a candy bar, a tube of Chap Stick, or whatever it takes to get a sturdy shopping bag with the store's logo on it. You could also plan ahead and pack a bag before your trip begins, or pick up a duty-free bag as you arrive.
When it's time to fly home, put your extra stuff in that shopping bag. Security won't care, and airline staff will assume you just bought something in the airport shops. On all but the cheapest airlines, that bag won't count against your carry-on allowance.
Now, this only works if you're not a jerk about it. You can't stuff that bag full of clothes so much that it takes up space that other passengers need. It has to look like a reasonable airport purchase and be just as reasonable to stow on board.
But you can use it for about a shoebox's worth of goodies—a pair of shoes, a few books, or whatever else you picked up that strained your luggage zippers past the max. This simple trick could save you as much as $100 in extra bag fees.
It's not against the rules. It's just a loophole. The airlines have gotten creative about charging us extra fees. So what's the harm in being creative, too, about your last-ditch plan to get your overflow stuff on board?