Acceptable ways to deal with rude and obnoxious customers...?

This one goes out to those of you who work of have worked in the public sector of society dealing on a daily basis with people who make you have very bad thoughts.
The basics of this is that I work in a cinema, and whilst I don’t mind the job generally the thing I find the most difficult is dealing with demanding people who invade my personal body space in order to shout and scream at me for such trivial details as; Being ID’d for a film they are clearly not old enough for (and not having any ID ironically), for not knowing the release dates of every film coming out for the next year and finally because the popcorn just isn’t salty enough (I’m not even kidding).
So what I want to know is how you all deal with similar situations and any particularly nasty experiences you wish to share and also if I am the only one who, when being shouted at by said customers, is thinking of various bad things that I’d like to happen to them.