You always have to specify "Washington state" instead of just saying Washington because of D.C.
You can taste the difference between Starbucks, Seattle's Best and Tully's.
You have an earthquake story, and so does everyone else you know.
You get pissed when you watch 10 Things I Hate About You, because you know that Stadium High School is not in Seattle. (And that paint balloon place has never existed at Gasworks Park, dang it!)
You consider Northern VA to be in no way similar to southern VA.
There are at least fifteen ways to get everywhere and you know which way to go based on the weather, time of day, current political climate, terrorism road closures, and whether you are coming or going. (This one cracked me up because it is sooo true.)
You have the Metro map memorized, yet act like you don't know when someone asks you how to get to Metro Center.
Use a soft J sound.
You don't consider exploding man hole covers to be an unusual occurrence.