Tips for petite statures:

Petites can wear a mini dress quite well. You won't lose your leg line, so you still look long and lean, despite your height. On a petite frame, be careful when it comes to a cute shift dress. They have less shape than a sheath, for example. Make sure the shape isn't so sack like that your frame gets drowned in fabric. And showing leg is important if you wear a mini dress because, without a defined body shape, you need to compensate with some visible skin in order to look sexy and proportionate.
Also, petites will have problems with the primary colors as well. They can make you look a bit childish when you are small to begin with. Metallics like brushed gold are another very big trend this season (both in clothing and accessories) and much more appropriate for a sophisticated look on a small frame. Remember, metallics are neutrals. They go with any color and they go with each other. You can mix all your metallics together!
Petite girls who wish to appear more elongated should try short skirts and capri pants. Avoid busy prints and cuffed pants, and try not to chop up the body with contrasting bold colors. Stay away from garments that are bulky or oversized, such as puffy bubble jackets.
What to Wear If You're Petite
Your Best Pieces

Time and again you've had the same problem: you find the perfect piece of clothing, but it was built for a 6-foot Amazon model. Ripples of fabric pool on the floor when you try on pants, skirts never hit your leg at quite the right place, and you have to continually fold up the arms of sweaters so you can see your hands. The obvious solution: start shopping in the petite section. All major department stores have sections full of clothes specifically designed to fit your proportions. At the very least, pick up a few petite-sized basics there: black pants, a tailored jacket, a coat that won't swallow you whole.
Overall, your shopping strategy is to look for pieces that elongate your whole frame. Monochromatic tones can help here: rather than breaking up your body into small pieces (short-waisted torso, short legs), a head-to-toe look in shades of dark brown or camel makes you look longer and leaner.
Can't Miss Pieces:
Long pants with heels You should have one pair of perfectly fitted pants with a hem that almost touches the ground when you wear heels. That way, no one can tell where your legs end and your shoes begin -- creating the illusion that you've got fabulous long legs.
Calf-length skirt and high boots Works on the same principle as the long pants. If the skirt and boot are the same color (black, brown, whatever), your lower body will appear taller.
Vertical lines You want the eye to be drawn upward when someone looks at you. So choose tops that have a vertical element. Subtle stripes, a zip-front jacket, even a long silk scarf that hangs along a jacket's lapels create this effect.
A shorter coat Stumble around in a long overcoat, and you'll look completely out of proportion. Instead, try coats that hit just below the hips. It'll show your legs and make your look more balanced.
Unflattering "Don'ts"
Big prints The bigger the pattern, the smaller you'll look in comparison. Go for smaller graphics, and wear prints on top rather than on pants and skirts to draw the eye upward.
Horizontal details Avoid anything that draws attention to the hem of your clothes (cuffs on pants, skirts that end with a ruffle). The effect is choppy, which makes you look smaller.
Sky-high heels You might think they make you look taller, but super-high heels on short legs look disproportionate. Don't go higher than three inches.
Big sweaters A loose top in a thick knit can swallow you up. Instead, go for more fitted shapes -- in petite sizes, please!
Ankle-length skirts If you want to wear a longer skirt, make sure you still reveal a few inches of leg at the bottom (or cover up with a high boot in a matching color).
Double-breasted coats They'll turn your upper half into one bulky, squat square. Not exactly flattering.