Reading a table happens within seconds of a waiter coming to a table. By asking for a cocktail menu or smiling and making strong eye contact, “they are saying ‘hey, I want to engage with you and I want you to make me feel really important,’ ” says Mark Maynard-Parisi, managing partner of Blue Smoke, a pair of barbecue restaurants in New York, owned by Union Square Hospitality Group. If people seem shy, “you want to put them at ease, say, ‘take your time, look at the menu.’ “

Blue Smoke does seven days of training with new waiters, five days of trailing an experienced waiter and two days of being trailed by the experienced waiter. Each day includes a quiz and a focus such as greeting guests.

With parties of four or more, “the most important thing is to read the dynamic between the group,” Mr. Maynard-Parisi says. Alcohol (who is ordering more or less) is a potential point of contention. He reads eye contact and body language to see if a group is friendly (looking at each other) or less secure, like an uncomfortable work meeting (glancing around the room, fidgeting). “Am I approaching the table to rescue them or am I interrupting them?”