Don't go in unless you have to. What should I say in a positive tone? I'm going to write a desk card, which means don't go in, but in a polite way,

It means that the invited person can come.

Only open to invited customers.

Or-an entrance with an invitation (posted on the door or the wall of the entrance)

A little tacky-VIP table

If it is in another restaurant or something, put a small sign on someone's desk-reserved, which means reserved for someone. No matter when she comes, others just don't need it. Until she comes to dinner or cancels the meal.