How we change what others think, feel, believe and do
Keep Them Hungry and Thirsty
Ensure they are hungry and thirsty, so they order more and so give a bigger tip as a percentage of that order.
Do not offer bread as they sit down, and certainly not before they order. If you must, do not give them a lot. Bread is very filling and eating this before they order may make them feel fuller and so order less or smaller dishes.
Salty or dry snacks
You can feed them salty snacks that make them thirsty, especially when drinks are expensive. Peanuts, potato chips and other bagged snacks often have a high salt content. Dry crackers or bread sticks also make them feel thirsty as these absorb saliva.
Salt may also be in the food, which will lead them to order further drinks. Pizza, for example, is often very salty.
Less filling portions
When large portions are given, unless they are proportionately expensive, this can lead them to feel full early and so not order later courses. Smaller portions are typically used in 'nouvelle cuisine' or other styles where smaller portions are laid out artistically across the plate. You can also make smaller portions seem larger with salad, drizzles of sauce, or other non-filling additions that fill up the plate.
We order as well as eat with our eyes and if they can see the food, they are more likely to order it. This is one reason why some restaurants have open kitchens, where you can see the chefs at work. You can also point out what other people are eating or even use photographs of dishes.
Another way of seeing food is to have a 'sweet trolley' where fruit, meringues, and other desserts are visible and can be served directly to customers. If you do not have a sweet trolley, it still helps to give the customers the dessert menu rather than listing out what is available.
If the table is unlikely to be needed when the customers leave, give them time to digest each course before ordering the next one. You can encourage this and even seem generous by saying that you will give them time to relax and enjoy themselves.
As tips are proportionate to order size, as much as you can keep people hungry and thirsty the more they will order and the bigger the tip will be.