How we change what others think, feel, believe and do
Give them a puzzle, game or problem to work in. If they need it, offer a pen or pencil (if this has your logo and phone number on, you can also let them keep it).
Rather than stand there and do it interactively, hand out the puzzle on paper. One way to do this is to hand out business cards or restaurant promotions with the problem on the rear.
Do this in a convenient moment when they are more likely to be interested in having something to do, such as when they have finished their first course and are waiting for the next course.
Different types of puzzle may suit different sizes of group. For individuals, give engaging puzzles like a crossword. For couples, try a problem they can work on together. For larger groups a puzzle they try individually then share the answer can work well.
If you get a lot of families, it can be a good idea to either have puzzles where the children can join in or have separate puzzles that will suit the various age ranges of the children.
This method might also be better when people do not appear to be engaged in conversation, although people who look like they enjoy a game or some fun can also be useful targets.
People in restaurants are not always so engaged in discussion that they do not welcome alternative means of entertainment.
Rind and Strohmetz (2001) got a tip increase of 18.5% to 22% by asking servers to give customers cards containing the following sentence:
FINISHED FILES ARE THE RESULT
The task was simply to count the number of 'F's. Many people get this wildly wrong as they count the 'F' sound, whilst the word 'OF' has a 'V' sound and so the 'F' is easily missed.
Rind and Strohmetz also tried getting the server to alternatively ask for the cards back or letting them keep it. When they let them keep the card, the tip only went up by a little (less than 1%).
Rind, B. and Strohmetz, D. (2001).