Depends on what kind of style you want and the price.
If you're worried about price, then thrift shops and places like Wal-Mart, TJ Max, Ross, Target, and K-Mart sell actually pretty descent stuff. People don't have to know where you get your clothes. There are a lot of cute stuff you can find in places like these that won't burn a hole in your wallet.
If you're really worried about style and brands and all that, I like shopping at Hollister. The stuff they sell there are based from being at the beach (perfect for summer). You can also try Forever 21, American Eagle Outfitters, and Urban Outfitters. They have a lot of cute clothes there and they even have look-books to see what kinds of styles and clothes look great together. But I must say that these places sell stuff that cost more than some places.