You ought to do two things beside eating in Times Square if you want to see famous people: walk up and down Eighth Avenue between 6 PM and 7 PM and watch the people who walk alone and not very fast. They often are theater people on their way to work. Those who walk in groups are usually people going to the theater, and people walking fast are commuters on their way to the Bus Terminal or Penn Station.
The other thing you should do is go to a Broadway show. Doesn't matter which one. Though, the more serious the show, the greater the probability of actors being in the audience.
Examples: While waiting on my pedicab outside Broadway shows that are letting out I have seen Valerie Bertinelli, David Byrne, Cromwell (forget his first name, the cyclist/actor who just broke his collarbone while biking), and Marisa Tomei.
Get to the show at least 15 minutes early, put something in your seat to mark it as yours, then go down toward the stage and turn around to watch people get to their seats. Famous actors have enough money to go see other people's shows. For, how to better learn the craft of acting, than to go watch other actors?
The more time you spend on the streets of Times Square, the more actors and actresses you meet. While biking on my pedicab I've met Jeffrey Tambour and Richard Salkind, on their bikes. They probably live in Hell's Kitchen, the neighborhood west of Times Square, which is loaded with theater people, or the Upper West Side, a 10-20-minute bike ride away. They both, by the way, wear helmets.
One night in 2004, while giving a pedicab tour of Times Square to two tourist women, one asked if celebs lurk about. We then came upon the actor who played the taxi driver on Mars, in the film, Total Recall. They were delighted. "Hey, man, I got four mouths to feed!"
Katherine O'Hara and Governor Ann Richards have been taken home in my pedicab. I did a promo for Showtime several years ago with Mario Cantone sitting in my pedicab in the middle of Times Square, on the traffic island where the Naked Cowboy usually works during the day.
For actually seeing actors at dinner:
A cop friend says Brian Dennehy eats at Angus McIndoe (W. 44th) on alternate Friday nights.
For actually seeing theater people and some struggling but fairly-well-known actors at late breakfast or brunch: The Edison Cafe, affectionately known as The Polish Tearoom, in the Edison Hotel's north side (at 47th Street). Take a booth, and look into the ceiling mirrors that allow you to see who's sitting at the counter. Do this on Wednesday, because shows start t 2 PM.
These are not promises. They are hunches based on past experience.