Well, the time is here! Submissions for the book are finally open! So send in those stories, please! Submit to email@example.com
I've said before that diners in the stories should be as much a character as the people in them. So be inventive. Just as no two people are the same, so are no two diners. Of course, they share a lot of common characteristics.
For example: a long counter with a row of swivel stools, a tile floor, a jukebox, booths by the window, surly waitresses and cooks, and usually some stainless steel, neon, or porcelain (depending on the type of diner).
A diner does not necessarily have to have all these elements. Nor does it need to have them in exactly the form I describe. Heck, it could have some stuff I haven't even thought to mention. But however your diner looks, it has to work in your story.
Your diner could look like paradise. Or it could look like a dive. I'm not so strict on how the diners look as long as they work for me.
That said . . .
Good writing . . . and good dinering!