I finally got my beta ass to do something right!

There's this little cafe in town near my school; I enjoy and frequent it quite regularly. Earlier today, I decided to once again visit the eatery. Now, I know what you're thinking, and you're right, I don't only go there for the food (Granted: the food is pretty good). I indeed have a favorite barista at this establishment. Every time I'm there, she's all smiles and waves. She's got all this good energy; and I don't know, she just seems cool. So at this point you're probably thinking why don't I just ask for her number. The problem was that I couldn't for the life of me tell if she was 19 or 25 (I'm a college sophomore currently), nor was I even sure she attended the University (I realize now that this doesn't really matter). So by wrapping myself in a blanket of meaningless(cowardly) questions, I never did the brave thing and just talked to her. Save for ordering my food from her heh. But, finally one faithful day, all by random happenstance, I struck up a conversation with her. Turns out she really had a bit to say, we then talked for a some time. I learned that she is a senior at my university, so she's graduating soon. Then I just took the plunge and asked for her number. She giggled a bit while she gave it to me, we said our good byes, and I tried my best not to jump for joy, and keep cool (more so for my own accomplishment rather than for the girl) while strolling out of that place.

I wouldn't say I want a relationship with this girl, but I wouldn't be opposed to something casual. She's graduating/leaving soon anyway, whatever happens will most likely be short lived and I'm ok with that.

So this brings me to my question. What do I do with this number? Do I text her tomorrow? Do I take her on a nice date, or just out to coffee? (keep in mind, she works in a coffee shop) What do I say? [More generic questions]...Etcetera.

TL;DR - I have the girls number, Now what?