It seems that the best way to convince Leonardo DiCaprio that you are right for a movie role, is to give him a good kiss. That is exactly what Carey Mulligan did, as she was trying to prove that she was right for The Great Gatsby role and it clearly worked, as she was almost instantly cast.

Scene from The Great Gatsby
Lurhmann explained, "So she does the scene, grabs him and kisses him. She went out the door and I was just thinking, ‘My God, that is Daisy Buchanan. I wonder what [DiCaprio] thinks.' He said, ‘The way Carey manifests Daisy is like something Gatsby would never have met in his lifetime, something so delicate that he would want to protect her to an obsessive and impossible level.’ And it was done."
Baz then went on to talk about his long friendship with Leonardo DiCaprio, saying, "I have known Leonardo since he was 19, he is a friend. When I met him he was a gifted boy. He is now a man, and he is a man completely in control of his powers. And he only has two things he takes incredibly seriously: the environment and acting."

Leonardo and Carey Mulligan in The Great Gatsby
As well as starring Leonardo DiCaprio and Carey Mulligan, The Great Gatsby also stars Isla Fisher, Joel Edgerton and Tobey Maguire. The Great Gatsby is set to be released on May 10 in the US, before then hitting the big screen in the UK on May 16.
The Great Gatsby movie trailer