All filmmakers have different ways of shooting a movie, and none are wrong. Some like to keep things basic and let the story flesh itself out on set, while others plan everything down to the last intake of breath. The latter happens to be 'Guardians of the Galaxy' director James Gunn.

James Gunn at 'Guardians of the Galaxy Vol. 2' screeningJames Gunn at 'Guardians of the Galaxy Vol. 2' screening

James Gunn has opened up about the secrets to the success of 'Guardians of the Galaxy', ahead of the release of the eagerly anticipated sequel. It seems the main thing that he believes is important when writing a script and shooting a film is as much preparation as possible.

'I've met very few directors who prep as much as I do', he confessed in an interview with MovieMaker. 'The final movie is much like the original conception. Every single thing is prepped. I started writing the script for Guardians Vol. 2 in August 2014, and the treatment was written a couple months after that. The script was finished months before we started shooting, which is almost never the case for a big spectacle film. I draw all my own storyboards. I work stuff out so I know exactly what the movie is going to be. I plan every single thing out, I plan for things going wrong, I over-plan. I'm crazy about it.'

Of course, planning a script in this way means that there's not a lot of improvisation going on in the scenes (at least not during filming), which is quite the testament to the quality of the actors that they can make written lines sound like throwaway ad lib.

'I'm a guy that believes in writing the script ahead of time', James continues. 'I rehearse a lot with the actors. If improv happens, it's much more likely to happen in the rehearsals than on set. Occasionally you'll find new moments, like a new camera move, or a funny line. But the role of improvisation is largely overrated.'

And it's not just about getting the script right either. James likes to have as many elements as possible sorted before beginning filming, and that includes the musical score. Because music is important to create atmosphere within a scene. 'We play the score on set - we even play it with dialogue, so I'll have the actors and camera people with ear buds in as we're doing the scene', he adds. 'Music is such an undervalued part of films, whether it's soundtrack or score.'

More: James Gunn signs on for third 'Guardians of the Galaxy' film 

'Guardians of the Galaxy Vol. 2' is set for release on May 5th 2017.