Help me talk to a boy!!!

Soo I work in a shop, there's this super cute guy who always comes in just for like a single drink, I've caught him looking in the shop as he drives past before now.

Everytime we see each other we are both grinning, he is forever looking back to smile again and hangs around to speak to me if I'm not with a customer...

But I'm super awkward never know what to say other than hi you ok!!!

What can I say to him!?!