One trade secret that actors often use to prepare for biography pictures is to spend time with the person they are portraying. Leonardo DiCaprio secretly spent several days with Frank Abagnale to prepare for "Catch Me If You Can," and Tony Mendez took Ben Affleck to some old CIA hangout spots during his preparation for "Argo."
But what if the character you're playing died 140 years ago in the Wild West? That was a question Val Kilmer had to answer when he played Doc Holliday in the 1993...