All depends on your local theater. I'd go to fandango and there should be an option to be emailed as soon as tickets go onsale for a theater of your choice.
For my local theater, it is a week before the movie opens. That is how it was for Wolverine anyway. My local theater is a Regal Cinema, if that helps. Though I did it through Fandango, I don't know if it changes based on how you reserve tickets.