Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

Actress Rosario Dawson (“Men in Black II”, “25th Hour”, “Sin City”, “Death Proof”, “Eagle Eye”, “Alexander”, “Percy Jackson and the Olympians”) walks the runway at the Fashion For Relief at Forville market during the 64th Annual Cannes Film Festival on May 16, 2011 in Cannes, France. (Photo by Ian Gavan/Getty Images)

First Place, Sports Photojournalist Of The Year. One of 24 photos by Patrick Smith, freelance for Getty Images: Sadie Bezzant is crushed by a sheep during the pre-rodeo entertainment of mutton busting during the Strawberry Days Rodeo in Pleasant Grove, Utah. (Photo by Patrick Smith)

A poster for the IMAX presentation of “The Hunger Games: Catching Fire” (left), and a teaser poster for “The Hunger Games: Mockingjay, Part I”, both created by the Los Angeles-based design firm IGNITION. Both are nominated for the 2014 Key Art Awards in the category of Theatrical Domestic One-Sheet. The Hollywood Reporter's annual competition for the best in film and TV advertising honors some of the most creative imagery used in movie posters. Here is a selection of some of this year's nominees. (Photo by Key Art Awards 2014)

In this April 4, 2014 file photo, a community policeman kicks a man who they alledge participated in an ambush against them near the town of La Concepcion, Mexico. The vigilante force was set-up by affected communities opposed to the construction of the La Parota hydroelectric dam. Two vigilantes were injured and one died. (Photo by Bernandino Hernandez/AP Photo)

Jury member Nicole Kidman attends the Jury Press Conference. (Photo by Vittorio Zunino Celotto/Getty Images)

Actress Angelina Jolie (L) and actor Jack Black attend the “Kung Fu Panda 2” photocall during the 64th Annual Cannes Film Festival at the Carlton Hotel on May 12, 2011 in Cannes, France. (Photo by Vittorio Zunino Celotto/Getty Images)