When you make a reservation at a restaurant, how much does the maitre d' know about you?

Quite a bit, probably. And we're not just talking your e-mail address and whether you're allergic to shrimp.

Restaurateurs are getting much more sophisticated about knowing a customer's preferences—and with competition in the business as fierce as ever, managers are looking for any way to keep an edge. "It's about being obsessive about hospitality and anticipating guests' needs," says Michael Welch, the general manager of BLT Steak in New York City.

Here are some of what the best maitre d's will try to find out about you before you even walk in the door.

1. What you look like. Julian Niccolini, the famed maitre d' at the Four Seasons in New York City, says he regularly uses Google Images to identify new guests, which allows him and his staff to greet diners personally when they arrive. 

2. How many times you've stood them up. Ann Shepherd of OpenTable, which handles online reservations for more than 15,000 restaurants, says the site does track data on diners who have a habit of blowing off their reservations. "If a diner has a certain number of accumulated 'no shows' their account is closed," she says. The system also notes—and prevents—a customer from double-booking at two different restaurants. 

3. What you ate the day before. New York City's Eleven Madison Park recently served a customer a mini lamb burger after he tweeted, "Burger King in the airport waiting for my flight to NYC. I'll consider this my amuse-bouche for Eleven Madison Park!" 

4. Whether you're going to get a freebie or not. You can become a VIP on OpenTable based on the number of seated reservations you book through the site. "Some restaurants will recognize the status in the service, by doing something like providing an amuse bouche," says Shepherd. But she stresses that VIPs don't get any special access to reservations on the site.

5. Whether you're cheating on your wife (or husband). Let's say you are a regular at a restaurant—and you regularly alternate between dinner with the spouse and dinner with, well, someone who is not your spouse. The great maitre d's discreetly take notice. "As part of our pre-shift meeting, we review the [reservation] books with the staff," says Welch. "And where there's a situation where a guest comes in with somebody new, it's 'Lovely to see you again.' It's not about what happened yesterday and who the individual was with then. We're not here to judge."