Oh, CocoLion reminded me of another one of mine: sports bras instead of cami's!

So glad I finally stopped in here - I was thinking of something else re: 'hacks'.

Anyway, I second the hair band around the belt to keep the end from flapping. I usually only do it when I have a jacket/sweater/vest over so no one can see. Maybe I need to invest in better colors . . .

I have a roll of Fashion tape and have used it to keep wide necklines actually taped to my skin so they don't get even wider and show bra straps.

I leave a little safety pin on the waistband of skirts that tend to rotate during wear. When I put them on I pin the top edge of the skirt to my hose or blouse or cami or whatever to keep the skirt in line.

The simple straight pin. It is truly multi-purpose and invisible when properly used.
I just put Fashion tape on my list!

Safety pins to keep the neckline of my wrap dresses in place.

Hidden snaps sewed in between buttons of button-down blouses to prevent gaping.

And most recently - a floppy pussycat bow blouse, where the top button gapes a little, but the great big bow covers it up!