I'm 16, very petite and curvy. My look is young but never trashy, slightly sophisticated but never frumpy, and not too trendy. Here are my favorite stores:
Pac Sun for jeans and shorts...I can almost always find something that fits me and they have a nice selection of washes, etc. A little on the pricey side though, jeans are usually between $40 and $50 and their tops are usually wy overpriced.
Nordstrom...they have a nice juniors section with really good accessories. Most clothes seem to be made for flat-chested girls though, which sucks for me :P They have a FABULOUS shoe department though.
Urban Outfitters...really cute pants, tops and accessories. Expensive, but the sale rack is my best friend
Victorias Secret...there is no other.
Express...Nice sweaters and dresses, and the ONLY place where I've found blouses that fit me! They have good dress pants too, but I've never found a pair that fits.
Free People...great styles all around. Some of their stuff is a little weird for me and it's definitely made for tall, skinny girls, but when I do find stuff that fits I love it! Super expensive though.
Gap...for relaxed, comfy clothes. I go there for basics.
Charlotte Russe...Some really cute styles, but not always the best quality. Lots of accessories and every kind of dress you can possibly imagine
That's all for now, happy shopping!