Turn Your Button-Down Into an Off-the-Shoulder Top
If you didn't jump on the off-the-shoulder train earlier this season, it's not too late to try the trend. Just take an oversized button-down, undo the first four or so buttons, drape it off of your shoulders, and tuck it into high-waisted shorts. Cuff the sleeves a couple times for maximum breeziness.
Replace Your Bag Strap With a Guitar Strap
Revamp a cross-body bag by swapping out the detachable strap for a guitar strap. Rebecca Minkoff makes guitar strap-esque versions, but you can also try shopping at music supply stores or on eBay for vintage styles. If you decide to go with the real deal, don't forget to pick up a few mini carabiners (Amazon sells packages for around $3) to attach it to your bag, since actual guitar straps don't come with convenient clips like Rebecca Minkoff's.
Put a Bandana on It
If your default summertime look is cutoffs and a plain T-shirt, a classic bandana is an outfit-changer. Tie it around your neck, loop it on your handbag handle, or use it to secure a ponytail.
Knot Your Shirt
Conundrum: you want to wear your high-waisted skirt, but all of your tops look weirdly bulky tucked into it. Knot your shirt, and don't think about it for the rest of the day.
Embellish Your Cropped Jeans
If you have a needle and thread, access to a fabric store, and an hour to spare, you can breathe new life into the cropped jeans you've been wearing all summer. Go dressy with feather trim, or try beaded fringe.
Mix Those Prints
It's the end of summer. If you're not going to take a few fashion risks now, then when? A couple of things to keep in mind when mixing prints: choose prints with similar color palettes, and the simpler the pattern, the easier it is to mix. So stripes are a great starting point.