When someone goes in for a job interview or is going to perform in a play, sporting event, or something like that we tend to wish them "good luck." The idea is that we want them to do well, and so we wish them luck in their endeavor. However, in Japan in the same situation you would tell the person "Ganbatte" (or "Ganbattekudasai" if you wanted to be more polite, but that may also be awkward westerner Japanese.)
Pronunciation: gone - bot - tay (like day w/ a t instead of the d)