Does your clothing style need a serious update? Forget the mall altogether and learn to mix and match cute clothes you already own!

[edit] Steps

Organize your closet/drawers. Put clothing in the correct categories. (Pants, sweats, jeans, capris, shorts, tops, tank tops, short-sleeve, long-sleeve, layered shirts, sweaters, hoodies, jackets, dresses, skirts, skorts, bathing suits, shoes, flats, boots, heels, pumps, stilletos, etc.)
Find a neutral-colored top and put it on. Toss on a cute cardigan or chunky beads to step it up a notch. Bangles, hoops, and lots of other costume jewelry pieces are not only inexpensive, but fun and pretty to wear.
Layer clothes and jewelry as long as it is not in excess and they go good together! You need to look not only spontaneous, but put together.
Toss on your favorite pair of jeans. Whether they're skinny, boot-cut, high-waisted, low riders, dark wash, ripped, or anything in between. Just be sure that they flatter your figure. Soft tummy? Tuck it in with some high-waisted jeans that suck it comfortably inward.
Don't be afraid to experiment with different patterns, colors, designs, and fabrics. That outfit combination that you look at in disgust may actually look good on you once you check it out in the mirror!
Stick with the basics. You don't need expensive brands to look good. Wearing a walmart or goodwill outfit is just fine if you know how to work it. Play it up with some nicer sunglasses, shoes, sparkly earrings, or oversized bag. Now stand up straight, throw your shoulders back, and rock that runway (or hallway...)

[edit] Tips

Don't wear under- or over-sized clothing. It will only look tacky. Your body looks better when it's not buried in baggy pants or suffocated with a tiny top.
Work with your personality. If you're punk, emo, or goth, then wear the chains and black. Preppy polos and put-together pieces might go for the populars. For more feminine types, delicate pieces might suit you best.
If it's a warm day outside, forget the jeans, grab your favorite skirt and add it to your outfit. Leggings under will look great, especially if the skirt is jeans.