Although I specialize in the securities law aspects of independent movie (and other business) financing, I also do "production legal" work when asked.
There are 4 stages of film production: development, pre-production, production and post- production. Each stage has its share of legal tasks.
Development: This stage focuses on getting the initial elements of the film in place. First of all, the property to be produced is selected. Legal counsel assists in securing the intellectual property. It could be rights to a story (which in turn becomes a screenplay) and/or rights to a script. Often a script is optioned, giving the producer an exclusive period of time to try to get production funding in place. If no deal is struck, the option expires and the project reverts to its owner or author. Sometimes a producer hires a writer to write a screenplay. This type of legal relationship is usually a "work for hire," where the writer's work product is owned, and later copyrighted, by the producer. If the producer or director is also the writer, then the rights to the project are transferred into the production entity.
The film's producer(s), director and star cast members are generally known as "above the line" personnel. Signing these people up is part of the development stage. Attorneys help with contracts for above the line personnel or assist in negotiatons with talent's agents in fashioning a workable contract.
Pre-Production: This stage gets the rest of what's needed on board in preparation for shooting (film) or photgraphing (digital) the film. Key personnel such as the Line Producer, Location Manager, Set and Costume Designers, Casting Agent, Director of Photography as well as other crew members including lighting, electrical, camera operators, assistant directors, sound personnel, hair & make-up... the list is pretty long. The rest of the cast is signed on. All of these production personnel are referred to as "below the line" cast and crew. Often times, an experienced Line Producer (sort of like the "foreman" on a construction job) will have her or his own "deal memo" forms that are used to sign below the line personnel. Production counsel works with personnel to be sure the legal documentation protects the producer's interests while, hopefully, still being fair to film personnel.
Locations are identified and reserved (using legal contracts). Insurance is purchased; liability and often insurance to help complete the film if needed, known as a "completion bond." Props and costumes are secured. Camera, film stock (unless a digital film), lighting, sound, construction, transportation and other equipment is rented. Licenses and permits are obtained. All of these involve a legal relationship between the producer and the 3rd party supplier. There's a lot for an attorney to keep track of during the pre-production phase.
Production: Now it begins; getting the movie on film or digitized. The producers and director make the schedule and coordinate/assemble the use of all the various production assets lined up to make the movie. Legal problems can arise if trouble develops with personnel, equipment malfunctions, accidents, disagreements.... legal counsel is at the ready; there's rarely a dull moment when making a motion picture.
Post-Production: Once production is complete, and sometimes during, a whole other set of experts are contracted to supply the finished film product. Editors, sound engineers, foley artists, musicians and composers for scoring, music licensing to include in the sound track, color corrections, "looping" (cast re-recording dialog where needed), special effects, sound mixing, etc. Sometimes producers hire a "post house" to do all of this in a package deal arrangement. Other times, the producer assemble(s) his/her/their team to put the finishing touches on the film. Production legal counsel reviews the contracts and deal memos with all of these people.
Film making is a collaboration of many people. In sum, if you're making a film, whether a feature or a short, be sure to obtain the services of an experienced production attorney.