This from the Open Forum Blog of American Express: 

Practice the "benevolent ambush." This tip for better customer service comes straight from psychiatric research that found people were more grateful for an unexpected dollar bill than they were for the $100 bill they knew was coming. Look for ways to surprise your customers with an extra benefit or bonus to build real and lasting goodwill. Try this idea:

• A random 50 percent off coupon sent via NetWaiter once or twice per year to each customer is a great start. 

There is a book called The Influentials, based on the premise that “one American in ten tells the other nine how to vote, where to eat, and what to buy.”

You know Influentials.  You have friends that are Influentials.  You have business associates that are Influentials.  You could even be an Influential.  Here are some common traits of an Influential:
•    They have a high profile in the community - local government leaders, those active in service clubs, high-profile businesspeople, etc.
•    They have lots of friends (Facebook and real friends).  They are always greeting someone, or someone is always greeting them.
•    They are everywhere - the Supermarket, PTA meetings, Little League games.  They just seem to be around.
•    People respect their opinions, often on a wide variety of issues.

Take special care of Influentials, because they can/will spread the word about your restaurant.  Here are some easy tips:
•    Always make a point to speak with them, even if it’s just to say hello.
•    Try giving them a complimentary sample of a new dish so they can talk it up.
•    Make sure your wait staff knows who these people are (and gets their order correct).

And, of course, talk up your online ordering capabilities.  A few minutes/comments can go a long way towards your bottom line.