A little microstitch "gun"

Get yourself a cute little microstitcher. This little guy is my "magic trick" for making clothes fit better, whether it's making sure a shirt doesn't gape, keeping my bra from showing, shortening straps quickly, or for a really quick mini tailoring job to make something more flattering before I have to chance to sew something. I use it at least weekly and always bring it when I travel. Also excellent for temporarily making my kids' clothes fit well before they've fully grown into them (e.g., shortening straps, long pants legs, etc.). This Avery one is a little more expensive, but better than others with a thinner needle and smaller stitches.