Its is primarily repetition, though keep in mind that a movie is shot over the course of weeks or months, so the actor only needs to memorize the lines for the particular scene being shot that day. They can also do the scene again if they mess up the lines, so it is easier than a stage play.
Some people just have a knack for it. When I was in HS theatre, I usually had all of my lines memorized within a week or so, and often had the entire _play_ memorized in a month. It is just how my brain works – it is _really_ good at remembering prose – I can still quote the ending soliloquy from _A Midsummer Night’s Dream_ from memory, despite not having been in the play for 25 years..
Folks that succeed in the theatre are going to be folks who have the ability to memorize their lines.
Latest Answers