(Fortune Magazine) -- "You're never going to believe this," a top executive from a major hotel chain told me, "but I just got walked from our hotel to this dump near Central Park."

It seems even hotel executives aren't immune from the recent surge of travelers showing up at hotels and being told there's no room for them. (Hotel folks call it "getting walked.")

It happens because, like airlines, hotels tend to overbook their rooms when demand is high for fear of not achieving full occupancy. Sometimes big-city hotels can overbook by as much as 20% (the average is about 10%).

That means even with a confirmed reservation, the front-desk clerk will send you to another hotel at the first one's expense--a headache for a busy traveler.

So how do you avoid this? Besides checking in early and being a member of the hotel's loyalty program, ask for a written or e-mailed confirmation when you book and bring it with you.

Then call to confirm two or three days before you arrive, get the agent's name, and ask to have your call noted in the reservation. And ask for a better room while you're at it--you have nothing to lose.