Unacceptable Luncheon Foods & Indulgences

DO NOT 

1. order any food that you have to eat with your hands e.g. hamburger, ribs, chicken wings. Ketchup and mustard makes an unsightly accessory.
2. eat potentially messy food such as pasta or salads.  Visions of spearing food with reckless abandon may make your lunch mate cringe in fear.
3. eat so much food that you find yourself sluggish during the meeting. If you have an expense account this is a real danger because you are probably eating better than you would at home plus a doggie bag is just plain gauche. Learn restraint. 
4. order alcoholic beverages unless your client chooses to do so first.  When selecting your beverage make sure it is one that won't effect your brain cells.  Slurred speech and bright eyes do not endear you to your companion.
5. order carbonated beverages.  Just think of the potential embarrassment caused by an inhuman belch.
6. discuss any topic that may bring about an impassioned response. This may be the one true time where discussing gun control is not welcome but may lead to violence.
7. smoke cigarettes or cigars even if the client chooses to do so.  I really don't think I need to explain this one.

In summary, eat as if your livelihood depended on it because it may very well be the case.