As someone who works in a restaurant, my advice would be not to be angry on the waiting staff if food takes time, it's does take time for you to get quality food, not something that has been in a heat storage for several hours.
And if your food takes extra time, and you see other customers getting their food before you, think about what you've ordered. Did you choose a well-done beef? Of course it's gonna take extra time over a rare steak, or a sallad or anything else that takes less time to prepare. Cooks can recieve up to 20 orders or more in a minute, depending on the type of restaurant and time of a day of course, but just remember that the ones working in a restaurant, are humans. Humans trying to do their best to please you.
And this one is for pretty much any kind of place that deals with customers in any way, like post offices, stores, restaurants e.t.c. If the one behind the counter tells you that they closes at a certain time, don't start with that "which time do you close?" and look at your own watch and claim "it's not ... o'clock yet!" The place has their own clocks that they follow, that they probably have to follow. Not your watch!