9. Follow the Golden Rule
Whenever you go to a restaurant, you should treat your waiters/waitresses and anybody else you interact with with the greatest respect and politeness. The sad and scary truth is that a surprising number of restaurant workers have admitted to spitting into or otherwise messing with the meals of customers that have been rude to them. Since your food is out of your sight with workers for much longer than it is within your sight in the hands of workers, being polite is important, even if the staff gets something wrong or is slow.