I like to immerse myself in the context of the project, read and reread the script, talk with the director, the screenwriter and the director of photography to acquire their thoughts and expectations.
I then start writing the themes, the main melodies, the upthemes and the arrangements, the harmonies and integrations with the sound design ... synchronize the melodies with the scenes, review, play back, turn off the audio and watch the silent scenes, then turn off the video and listen to the music, to review the scenes in my mind and understand ...