A movie begins with a producer. Producers are often in charge of looking through scripts and finding one she thinks will work well within the framework of a film. A movie producer may find a book she likes and commission a writer to turn it into a film script, or may wade through submissions of writers for original scripts. The producer's job is then to help the writer make the script workable.
One of the biggest jobs for the producer is to work out finances. He must do this before he hires actors or a director, or begins to look for locations to shoot the film. The financial aspect will inform all of these decisions. The producer must also solicit money from the studios or from private benefactors to help make the film. This process can take a few years and will begin long before the first actor is cast.
A producer is in charge of hiring everyone from the actors to the director. The crew is usually hired first and then they will help the producer choose the appropriate actors for the roles. The decisions on who will work best for the film depend on how much money the producer was able to raise and what everyone else involved in the movie thinks would work in the best interest of the film itself.
The producer is often absent during the filming of the movie, but will reappear for the post-production process. This will include editing and music, combined to help portray the director and producer's version the most accurately. The producer will work closely with the editors and composers to create a few versions of the film and together they will decide which works best.