The best way to start a conversation is to refer to something from the conversation you had with her face to face.
But if you don’t know anything about her other than she is cute then it is better to play it safe, don’t over think it just keep it simple.
You have to be witty, playful and charming in just a sentence or two, and once sent, there's no way to take a text back. When you're trying to think of something flirty to text your crush, you should try to think of something no one else but you could say.
It shows that you're not texting just because you feel like it, but because you want to keep a conversation going and that you care what he crush thinks.
Keep these in mind when you ask questions: This may seem trivial and unconnected, but if you were flirting with your crush in person, then you would make sure your outfit was neatly put-together and that your hair was in place. Try not to go overboard or your crush will be able to see that you're trying too hard.
It will help you to distinguish yourself from those other guys who are texting her.
Or rather ask her a question about something that you both talked about earlier.
Texting is huge, especially if you're trying to win someone over.