How we change what others think, feel, believe and do
Persuade people over a meal. When they are eating (not before or after), present your ideas and make your persuasive statements.
Make sure the place where you are eating is pleasant and comfortable, and that the food is of good quality. It is key that the other person is comfortable and feeling satisfied.
A sales person takes a customer to a nice restaurant. During the meal, they ask more probing questions about needs and then sows some seeds about future problems. At a later meal, the sales person finds the person more open and starts to talk about a possible solution.
Gregory Razran described this principle in 1938, when he presented political statements to subjects, first in a normal setting and then in other contexts. Statements rated during eating a meal increase significantly in approval.
One reason this may work is by an extended effect of the urge system, where hunger creates an urge to eat, and whilst we are eating we may more easily take in ideas as well as food.
If there is alcohol at the meal then this may also impair normal judgement, though this is not a necessary addition -- the major reason the Luncheon Technique works is food and eating, not drunkenness.
Having lunch with a person takes a certain amount of time, typically around an hour, which is often more than you might get in a sales meeting. You also have a captive audience who is not distracted by other intrusions.
Note that this is an incremental factor, not a magic technique -- if the person fundamentally does not like your ideas then eventually .
Razran, G.H.S. (1938). Conditioning Away Social Bias by the Luncheon Technique, Psychological. Bulletin, 35, 693