Tonight, millions of americans are planning holiday travel. And we have some confidential advice, from hotel workers, garage attendants. 20/20" anchor chris cuomo is opening the door on what could... See More
Tonight, millions of americans are planning holiday travel. And we have some confidential advice, from hotel workers, garage attendants. 20/20" anchor chris cuomo is opening the door on what could really be happening behind the scenes during your vacation. Reporter: Looks like a car-jacking, doesn't it? But it is actually a car parking by a hotel valet in st. Louis posted on youtube. The valet's not going to make any money unless he gets that dollar tip. So -- so there's a focus on speed. Of course, when it comes out, it's driven really slowly and carefully. Reporter: The solution? Tip the valet before you surrender your car or expect the abuse to begin. When it comes to hotel happiness, tipping is worth it. Come to the front desk with your friend president jackson and an upgrade could be yours. Flash a 'tude instead, watch your back. Is it true that there is a culture of revenge that exists on behalf of the staff? Oh, without a doubt. There's a thousand ways that i can get back at you for something you don't even know you did. Reporter: For example, in new york city, where the area code is 212, you may be put in 1212, which is exactly what a guest f forgetting to dial 9 for an outside line, would dial. If I put you in room 212, it's a beautiful room by all accounts. However, there's a punch of idiots all through the hotel that don't dial out and it's going to ring 1212 all day, all night. Reporter: And a nasty attitude is a big motivator for staff revenge. Rude of cheap guests are being watched and secretly listed as a pita, or a pain in the -- obvious. But if you're a big tipper, they may have logged you as an f.O.B., Or friend of ben, as in franklin. prompt attention. But cash doesn't guarantee character. Look at this video shot by some hotel guests. In comes the lhotel manager, in hi goes to the staff, and out goes their cash. Cautionary tale. Doesn't usually happen. To sum up, when you travel, leave the bad attitude at home and, diane, every little bit helps. I have no attitude, chris. Reporter: You are perfect. Of course. Stipulating that. Other tips coming up tonight, for instance, about how to reduce the charges? Reporter: Here's a good one. Now, diane sawyer may not do this, but chris cuomo might. The movie that you've watched, the thing that you've eaten in the mini bar, if you challenge charges, they are very much in the h business saying, the customer is office right. Within your own ethical standards of what happened or did not. Very different for the two of us. But if you do challenge, may wein. Watch tonight and see how the
This transcript has been automatically generated and may not be 100% accurate.