Amanda Kludt, editor of Eater:

Be exceedingly friendly. That means (cringe) introducing yourself. Asking people their names and remembering them. Introducing yourself again. And again.
Tip well.
Have a go-to order.
Dine during non-peak times.
Go a lot within a short period of time.
Sit at the bar or counter.
If you are going to sit at a table, make reservations so they can track you.
If there is a host or greeter, get to know them. They are paid to remember faces.
Make a reservation on your way out.
Ask about what to order. Talk about things on the menu (or that came off the menu that you miss).
If there are other regulars, make small talk with them.
If you order a bottle of wine, offer your bartender or server a taste.
Go on the same day of the week to get the same staffers. Home in on one person and cultivate that relationship (but don’t be a creep, obv).
Go alone and try to stay off your phone.

I can’t underscore the value of having a few go-to restaurants, especially on days when you don’t want to cook or eat at home. The greatest luxury in life is to eat by oneself, without being bothered and taking a few hours out of a crazy life. Why not do it in places where they treat you with love and care. And you can do that by being a regular. I am regular at about four restaurants in San Francisco, and one thing I do is get to know people and their lives.