Short answer: open-ended questions, that is, anything that will get greater response than a curt "yes" or "no". Example: instead of "do you like this music?" form the query to invoke a longer answer: "what do you think of their (latest) CD?"
Longer answer: what do you want to know about her?
Asking her about opinion, that is, what she thinks (about... whatever) will often get a conversation going. Make your own statement and ask, "what do you think?", "do you agree?", "what's your opinion?" Lots of ways to do this, including the assertive: "tell me".
I'm not a kid, so it wouldn't occur to me to state come-on lines (you're peers can tell you best about that). But I can tell you that a grown woman's attention snap's-to pretty quick if a man displays that he actually "hears" what is being said. Astute communicators use eye contact (up at the eyes, please - you'd be surprised how many guys forget to fully engage) along with echo comments beyond "oh" or "okay" by use of reflection: these are short-short positive sentences, or sentence fragments, relevant to what is being said. Yes, I agree that many fellows get by with the ubiquitous "uh-huh", but guarantee you the successful ones were sure that they grunted WITH eye contact. By the way: these responses don't have to be in agreement, they are used to acknowledge that you comprehend what was said. Further useful skills include redirection of topic, as you wish new input (a gentleman that wants a lady's attention never initmates that he was bored, just curious about another aspect) - or are suffering way too much intel about a subject (e.g. you like her nails but didn't need to know six ways to build them; or you wanted to know the sit-rep (situation report, that is, where things stand now, but don't need a full reconstruction, a-la an hour of he said-she said). In fact, many men, after learning how to invoke conversation, concentrate on how to gently direct it, then how to operationally disengage with finesse. REALLY listening, learning to acknowledge, helps to wind up supportively, leaving an open door of familiarity to begin another time again. A gentlemanly humor is incredibly useful; that is built with your own style, but with a kindliness to the girl. Good luck to you.