What's a good but small conversation starter for a hallway chat! I need to know!!!?

[I'm that guy]

Well I have this girl in this one class and I don't have time to talk to her except for in the hall way for like 3 minutes. And thats better then nothing. So when can I say to her to start a convo then go to our next class. Thanks.
Yeah but I just wanna talk like 3 minutes straight to her with no akwerd silent moments. I'm not shy around girls, but I'm usually talking to them for hours. I don't know what to say on a short convo.