Format your screenplay montage correctly to let the director know that it is a montage. For instance, Script Frenzy explains that a montage can be set apart on the page, with the title of the montage above a list of shots, and a note that ends the montage. You can also have a montage title and beneath it list the master scene heading next to the action.
Reconsider using dialogue and voice-overs in your montage; they can be distracting. The point of the montage the succession of scenes. The producer or director might choose music to put behind the montage. The music should make the montage increasingly important to the script.
Write the screenplay montage with purpose. According to About a Screenplay, a montage should have information that needs to be conveyed quickly, contributes to the story and moves the plot forward. Read your montage several times, and rewrite it until you are positive that it is an important piece of your screenplay.