Only do this if the situation warrants it. You'll scare a lot of girls away by being so up front, whether they think you're cute or not. They may be struggling with confidence issues too and not really know how to reply back to you, causing a mad awkward situation.
Compliment something about them real quickly and don't press the conversation. The'll usually continue the conversation if they want to. Or find a common interest. Clothing brands, band t-shirt maybe, text books, etc... Pretend you like something if you have to (later on you can tell them you pretended to like something just to talk to them, and they'll love it, trust me). You're just looking for common ground to begin a conversation.
On that note, it's about time I asked for a "Ladies Men" cult invite. Anyone want to hook one up?