"Hey this cute girl is talking to me, but I don't know how to flirt with her. Help?" If you can use any references to your conversation, that would be even better. This is also called callback humor.
In most cases the girl will check her phone and she will see you texted. Now you have to pretend like you know nothing about it and you just keep the conversation going. She will usually text you back something funny and you can do this flirting back and forth while you both pretend nothing is happening. What is so great about this is that you two already have some text messages going back and forth even before you two go separate ways. So the next day when you text her, you don't start from a completely cold interaction because she already has a chain of text messages in her phone. This technique will make a lot of your phone numbers solid and help to make sure that a girl responds to your initial text message the next day.