Interesting article from the Wall Street Journal:
The Signals You May Be Sending
If a waiter reads the needs of your table correctly, you're likely to end up with a good experience. Inadvertently giving off the wrong signals can doom a table to service that's too rushed, too slow or just off kilter. Here, how to work the system.
If you're chatty... A waiter is more likely to assume a friendly, chatty table is there to party. Get ready for more offers of drinks, dessert and a talkative waiter.
If you act moody... You may get better service. Several waiters said they are more careful to get every detail right when they believe a table is already in a bad mood (a couple fighting or a tense business meal perhaps).
If you say 'It's OK'... To attentive waiters, saying food is 'OK' is a red flag that you aren't happy with your meal. The waiter or manager might dig for more information to fix the problem.
If you ask about the menu... Food questions are a sign that you either like learning about everything you might eat or you feel lost and need guidance. One menu question could lead to a long, full menu description. If you seem overwhelmed, the waiter might try to steer you toward a particular order.
If you grab the wine list first... Expect the waiter to focus wine explanations and questions about refills to you.
If you're early and fancy... Diners who are dressed up and have an early dinner reservation may lead waiters to suspect they have another event that night and serve them at a fast clip.
If you're wearing a suit at lunch... Diners who look like they just stepped away from their cubicle, whether in a suit or business casual, are bound to get speedier service. The exception: If the waiter realizes the boss or valued client wants to set a slower pace by asking for more time before ordering or pulling out papers for a sales pitch.
If you act like the ring leader...
A waiter will try to determine who is in charge at the table through body language, clues in conversation or by who made the reservation, and defer to the wants of that diner.
If there's no obvious leader...
If no take-charge person emerges at the table, the waiter may struggle to figure out whether to be chatty or invisible and whether to make the service quicker or more leisurely.