Matt Damon tells jokes before walking the red carpet.

The 'Informant!' actor finds laughing just before he arrives at an event makes him seem more approachable, and also helps him keep smiling.

He said: "The trick is to tell a joke just before you walk out there. There's a lot of joking on the red carpet because it is a surreal thing and you need that."

The 38-year-old star added he finds the whole process of attending premieres and other Hollywood events and "unnatural" as he is forced to speak to people he doesn't know.

Matt recently spoke about his role as overweight Mark Whitacre, an agricultural businessman who becomes an FBI informer, in new movie 'The Informant!'.

The actor piled on 30lbs for the film, and loved every second of it.

He said: "It was very, very easy to gain the weight. It was very, very fun, probably the funniest time I had working because I didn't have to go to the gym after work and I just ate everything I could see. It was absolute heaven."