You shouldn't need to really rely on canned stuff - don't walk up to her with a mental list of what you're going to say.
It will be much more natural, and easy, and comfortable for both of you if you just use situational stuff - look around you, what's odd/funny/weird going on? Is there something cool about her clothes? What about tests - how did she think she did on the last one in math? How did you do in math? Isn't math stupid, when will you use this in the future - the last time you used math was trying to see if you could afford a $3.99 shirt at Old Navy - has she ever seen the bargains there? What's the best deal she's gotten on shirts, does she know where you could get some good ones?
Just...it's natural. Talk to her like you talk to anyone, just don't swear up a storm, keep the language clean, and let it flow naturally. You might get a dead spot or two in conversation - just learn from your mistakes and get better as you go along.
