I hate to admit it, because I know that two wrongs don't make a right, but ordinarily, I am rude right back so that the person who is being rude to me will know exactly what it feels like to be on the receiving end of rudeness.
I usually take the high road, and continue to be polite, hoping that they will catch on, realize they are being rude, and then treat me politely, just as I am treating them.
It kind of depends on my mood. If I am in a bad mood, I will be rude toward whoever is rude to me first. But if I am in a good mood, I just ignore their rudeness and assume it will come back and bite them at some point in the future.
I usually will call them out, and say, "Excuse me, have I done something to justify your rudeness toward me?" They will usually be taken aback, apologize, and then act civilly.
I usually say, "Hey, what's up with the attitude? How's that working for you? It sure isn't working for me." That almost always makes the person take a step back, assess their behavior, and then adjust it accordingly.
Compiled by Nancy, Jenny and Katie Lyness