Zaz wrote out a nice scenario in the book ("How to Avoid Arguments", page 174) on how a foul/contest should go. In brief, it portrays two rational people debating the merits of the call. Here are some ideas on how to get your opponent to be rational.
1. Avoid hyperbole. (dictionary.com defines it as "(a) figure of speech in which exaggeration is used for emphasis or effect.") Starting off with "that is the worst call I've ever seen" almost always leads to a do-over.
2. Don't take it personally, and don't make it personal. Calmly dissociate yourself and your opponent from the actions, as if it were two other people that were involved in the call.
3. Get over your anger immediately, before you say a word other than "Foul" or "Contest."
4. Give up after 30 seconds or if you repeat yourself more than once.
5. Consider that the other guy may have a point, and that whatever happened may not have been intentional.
6. If all else fails, knee him in the nuts and run away.