Note: After this article ran, readers submitted many more examples of bad travel behavior (including their own). The second article in this series, which arguably has even worse examples, is here.

Once upon a time, they say, business travel was fun. Now it's cutthroat. It's not just what the airlines and rental car companies are doing to us. It's what we're doing to each other.

I met a guy who says he gets two seats for the price of one on long train rides. His trick is to buy beer in the station, puts a few cans on the tray table, and stare like a fake drunk at whoever starts to sit next to him. Result: He spreads out; everyone else crams in elsewhere.

We live in a sorry-not-sorry world, it seems, so I wondered if there was more stuff like this going on. I started asking around.

Here are some of the other self-serving tricks I learned about. Many are tactics for trying to get more room on airplanes, trains, and busses by encouraging others to skip the empty seats next to them. I've ranked them backwards, in order of how annoyed I suspect you'd be to learn the passenger in line in front of you was using them.

1. Scare off other passengers by faking a fight.

Several passengers I contacted admit to putting down bags or papers in hopes that people like you would be dissuaded from asking them to move. But some travelers use more creative tactics. Take Laura Cody, a travel blogger and YouTuber, who says she and her fiancé stage fake fights to ward off other travelers.

"We pretend to argue just loud enough that other people know what's going on," Cody says. "We then usually take three seats if it's a plane (that's not fully booked) or four seats if it's a bus and our excuse is that we need some space away from each other for a while."

2. Block the seat in front of them...

Several people suggest using the Knee Defender. The problem is that it's not allowed on many flights. So some passengers use a less-obvious method.

Kallen Diggs, author of the book, Reaching the Finish Line, says he skips the controversial device and instead uses a "steel carry-on" bag that happens to fit exactly between his seat and the seat in front of him. "The tight fit prevents the person in front of me from reclining their seat."

3. ...Or recline before anyone can block them.

Call this one a preemptive recline: "The flight attendants come through and make you move your seat to its upright position," said this traveler. "As soon as the plane leaves the ground, I lean back before the person behind me can stop me. That way you have gravity working with you. It might even break the [Knee Defender]."

4. Carry something sharp and dangerous.

This one is more of a commuter's trick than a business traveler's trick, but working in New York City, I can see where Meghan Calak is coming from:

"The L train that runs from Manhattan to Brooklyn it is almost always unbearably crowded," writes Calak, who says she's traveling the world these days but used to work at LinkedIn. "One of the best ways that I've found to keep my personal space during rush hour is to bring along a small potted cactus and hold it in front of me. .... No one dares bump into me."

5. Look for stuff to complain about.

Elizabeth Aldrich, who used to fly weekly for her corporate job but now travels a lot for pleasure, has two tricks. The first Is to be on the lookout for things to complain about.

For example, she says, "if anything isn't functioning with my seat (the in-flight entertainment doesn't turn on, or the seat won't recline), I make sure to (nicely) complain. Usually they will give me a drink ticket or two. Once I even scored an upgraded seat."

6. Fib for free booze.

Here's Elizabeth's other trick. While just about every travel advice article suggests not drinking alcohol on flights, that advice crashes right into reality when you start asking people what they really do. For example, they like to drink.

"I am all about getting free alcoholic beverages on long flights," Alrich says. "It's actually incredibly easy to get flight attendants to 'forget' to charge you for your drink orders. ... On redeyes, I casually drop that it's my birthday ... The more shameless version of this, which I have tried once, is to look sad and say you're going to a funeral."

7. Build a privacy screen.

I've never seen anything like this, but it would be kind of a weird idea to make up, so I'm going to pass it along. Sebastien Dupere, CEO of Dupray, which sells steam cleaners and steam irons, says he carries a small roll of duct tape with him.

"I tape my blanket to the ceiling to create a 'screen' or 'barrier' [against] the person sitting in the middle seat (I always sit window!). It gives me the peace, quiet, darkness, and privacy that I need," he says.

8. Cut to the front of the taxi line.

This one is for saving time when you reach your destination, need a taxi, and find there's a long line for the cab stand (assuming for whatever reason you can't use Uber).

"Forget this," says Travis Bennett, founder of Nomad Stack. "Rip the airline tags off your baggage and head to the departures section of the airport. ... If security asks what you're doing, I tell them I need to meet my wife. Now you've just got to hang back until a cab drops another passenger off. Once they're sorted, say hi to the cab driver and ask if they can take you. Nine times out of 10 they'll be more than willing, and you'll be in a cab en route to your hotel in under five minutes."

9. Cut to the front of the volunteers line.

One of the only times you can get something for free from an airline these days is if you're willing to give up your seat on an overbooked flight. Often, it turns out there are more volunteers than needed.

"When ... the airline offers an incentive ... I will shamelessly bolt to the counter," says Brian Hayes, who describes himself as a 23-year-old journalism graduate working in technology public relations. "I've never directly cut anybody in line, but I've beat people to the counter right as they're approaching it. The airline usually only needs one or two seats to be freed up, so it can be cutthroat."

10. Be a shameless gate lurker.

Nobody I spoke to actually owned up to this behavior, which is funny because it's one of the most common things I see people doing in airports--and that veteran travelers complain about.

"'Gate lice,'" wrote The Wall Street Journal a few years ago, "a term used to describe passengers who clump together in front of the gate before it's their proper time to board, seems to have been gleefully adopted by some of the road warriors who chatter on Flyertalk."

11. While we're at it, sneak into lounges.

Apparently, this is the practice of being "door lice" or "lounge hitchhikers," of standing outside airline lounges and harassing members to bring you inside as a guest. I've never seen this myself, but was referred to a travelers' blog that talked about it.

12. Pretend to be disabled.

This one sounds pretty horrible, which is probably why nobody who says they've done it was willing to be quoted. However, I've heard about travelers--always a friend of a friend, it seems, so maybe that's heartening--who carried a cane or crutches after they no longer needed them. The point, of course, is to entice a gate agent to let them board an airplane early.

13. Lie, and then lie down.

I'm not sure how often this would work now, since airplanes are so often completely full. However, comedian Dan Nainan says he checks the seat map just before boarding to see if there are any rows with nobody assigned seats in them.

"I'll go to an empty row and sit on one end and put my bag on the other and if anyone comes by, I'll tell them the seats are taken," Nainan says. "This way, I am sometimes the only person who gets to lie down while everyone else has to sit upright."

14. Spill water on the seat next to you.

How bad is this? One passenger admits to intentionally pouring water on the seat next to her, just so she can discourage other people from sitting there--but making it sound as if she were only doing so for their own good.

"This is when I really want to be able to spread out," she says. "If anyone tries to sit, I say, 'You might want to try another seat because that one's all wet,' and 'I'm not sure if it's just water...' Nobody wants to take the chance. Of course, once we get going I just wipe it up and spread out."

15. Make yourself smell bad.

Call this one the Skunk Trick--intentionally skipping a shower or wearing dirty clothes so people won't want to sit next to you. One traveler says he came upon this trick by accident, at least to begin with.

"I was with a bunch of friends for the weekend [in Las Vegas], with a 7 a.m. flight on Sunday morning," he says. "Hung over, wearing the same clothes ... People actually moved away from me."

Removing your shoes will probably also accomplish this olfactory defense, as will bringing pungent food aboard. "It's the only time I eat Burger King," confesses one traveler.

16. Just be a jerk.

We hear about people who flat-out get belligerent on planes. Often, they're treated with kid gloves afterward (see the story of hotel heir Conrad Hilton III, here, if you really want to get your blood boiling). But Eric Bowlin, a real estate investor and writer, offered this anecdote about what happened to his wife when she was coming home from a trip overseas:

"She was traveling with a 2-year-old toddler and also while pregnant. The flight attendant noticed this and began moving her to [a] row with three open seats so the toddler could lay down and [she] could have some room to recline or rest her back during the 14-hour flight.

Right before they got seated there, a man moved from another seat and took the whole row. ... The attendant asked him to move back to his seat ... When it was explained to him that my wife was pregnant and had a toddler, he said he didn't care and he wanted to lay down. The worst part--the man never actually laid down."

Note: After hearing from readers after this article was published, there's now a Part II: 12 Even More Selfish Things Other Travelers Do at Your Expense, Ranked in Order of Despicableness.