Next time you say hello, add that "I didn't catch your name, I'm Josh?", then repeat her name to be sure you got it correct. Next time you see her, say "Hi Sarah" then add something about the weather or traffic or ask where's a good place around here to get a good burger, taco, pizza whatever. Girls love to help a guy out. You have to start talking if you're going to work your way up to asking for her email. Which is what you'll want to do before the end of the month. Asking for her phone number or more, may be to soon (unless she gives you a sign). I think it's safe to ask to keep in touch with an email now and then. Something could develop there. Don't let it go without trying. If she says no or gives you the cold shoulder than at least you tried.