Confirm the overall lighting style you want for your film. Base this on your vision for the story, primarily how you want the scenes to look on screen. For instance, you may want a generally high-contrast lighting, a glossy lighting like most TV commercials and epic blockbusters or cinema-verite or documentary-style lighting for the entire film or for specific parts of the film. When making your final choice or choices, consider your production budget and the available lighting equipment you can use for the production.
Finalize the list of lighting sources/equipment you need per shooting day. Base your list on the location and artistic requirement of each scene. If you have enough financial resources to rent out professional lighting equipment in a production rental house, request quotes from rental houses until you find the best deal. If you want to use available resources using practical lights that are typically accessible inside the home or the office, check where you can find or borrow them ahead of time.
Bring the lighting equipment you plan to use on the movie set, once the art department finishes setting up all props and other art requirements. As a basic guide, film lighting uses the basic three-point lighting setup. In general, lighting a film needs a main source of light called the key light, at least one fill light, which is a more diffused light to help support and blend out the key light in the scene, and a backlight, which helps separate your main subject from the background.
Position your key light on your desired location on the set. This can be outside a window, on one side near a lampshade or on the top-center of the actual scene to be shot. If the scene is set inside a room near a window during a mid-afternoon time frame, the key light is typically the sunlight coming from the window. And so, your key light should mimic the quality of sunlight and make sure this registers well on the film.
Position your fill light on your desired location on the set. This helps illuminate the face of your actor or any other important object shown on the scene. This type of diffused lighting lessens the shadows coming from the stronger key light. The fill light is generally the same type of professional or practical light source as the key light, but its intensity is decreased or a diffusing paper is placed in front of it to better scatter and diffuse the light. The diffuser is typically attached to the light using an ordinary or production clamp. Placing the light farther from the scene also makes the light softer for fill light use. Others bounce the light from the ceiling for a more-diffused look.
Position your backlight on your desired location on the set. Choose a specific area on the scene where you want the backlight to be seen on frame. This is usually on any of these positions: top-left, top-right, eye-level left, eye-level right, bottom-left or bottom-right of the set. The exact position where you place your backlight determines where the lighting contours on your actors and props will be seen.
Rehearse the scene complete with your intended lighting setup, actors and any props they need to bring with them during the scene, if any. This way, you will be able to adjust your three-point lighting setup as you know how the actors would move around the scene. Finalize your lighting setup according to the result of the rehearsal.