Exaggerate one story and every story after it comes with a discount.

Credibility is one account, not one per story. Stretch a number for a better laugh and the people listening quietly adjust everything else you say downward, usually without mentioning it. The irritating part is that your true stories are the ones that suffer, since those are the ones that needed to be believed.

Notice where you inflate, since it is usually the same spot: how many, how fast, how close you came. Try telling it flat and see that it still works. When somebody calls you on it, agreeing immediately costs much less than defending the bigger version.