I wouldn't go with the "hi, how are you?" approach because that could turn awkward extremely easily. If possible, make the reason behind the encounter a bit more natural. Try sitting a few seats away and then come up with a banal reason to talk to her: borrow a pen, ask for the time, request clarification about something on the syllabus, etc. Try doing this a couple of times over one or two classes. Once you have a reason to be talking to her, that's when you can throw in some small talk and ask her name/program/whatever and then engage in some low-key flirting. You'll know if she's interested.
But yeah, approaching someone in a class is way more awkward than doing it at a bar with the aid of the social lubricant that is booze.It took me the better part of a semester to get on talking terms with a hot Asian guy from my Expository Writing class... but it was woooorth it.