As mentioned in part 1 of this series, production really begins with a production greenlight (which may come at the same time as preproduction greenlight, or only afterwards, depending on the project.).
For bigger films, this is dependent upon getting a go-ahead from the financial backers (a greenlight from a studio executive for a studio film, or delivery of materials that convince indie backers to go ahead and release funds promised). For no-budget films this is when you decide: "hey, I like what we've gotten out of prepro, let's go shoot this thing now."
Prior to going on-set, production includes the tail end of pretty much everything going on in preproduction. Indeed, the distinction between late preproduction and early production is debated. If you mark a production greenlight as the start of production (as some studios do, and I am using in this series), then these tasks happen during early production. But if you mark the first shooting day as the start of production (as others do), then what I'm calling early production is instead late preproduction. Either way, the tasks you must perform are the same.
Here is a visual guide to the first phase of production, followed by a summary of the process (the parts that weren't already covered in the preproduction article, which are included in the diagram since finishing those tasks likely will carry-on past the production greenlight):
Casting, Wardrobe, Make-Up Tests, Rehearsals, Camera Tests with Talent
Sign those final contracts with all your remaining actors as quickly as you can, because your schedule depends on it (and depending how large a percentage your casting cost estimate is relative to the rest of your budget, you may not be able to budget for crew and materials until you do this).
The final casting is also needed so you can start rehearsing (and doing those last script tweaks before hitting the set), fitting costumes (and working with the production designer to refine any costumes that aren't working now that the real talent is selected), doing make-up tests, using real talent in camera tests to start finalizing lighting and film stock choices (some talent, particularly big names, won't allow this -- and/or you can't afford it), getting to know people so you can develop a working rapport with them, and (and this is serious with regards to primary cast and crew) finding out about dietary restrictions before starting the process of hiring a caterer.
Rehearse as much as you can afford, financially (unless you or your lead are the kind of folks who absolutely hate rehearsing -- in which case, I hope you're both excellent under pressure).
You're about to go shoot a movie. On-set work is the post people intensive part of the filmmaking process, and now you've got to go out and hire the entire rest of the crew (actually, the production staff and department leads you hired in preproduction do).
For a large budget film, you may be about to hire and schedule several hundred people. Everyone from the most senior craftsmen and technicians to the lowliest P.A. need to be signed-on now so that legal and payroll can get them on the books, and production (First A.D. and Line Producers) can get them onto the schedule, and production accounting can start itemizing this part of the budget.
In reality, big productions do the entire budget and pre-assign salaries and schedules, and then people either agree to take the jobs or not.
No-budget shooters on the other hand need to be more flexible with timing and compensation because you've got as much of the latter as you can squeeze out of people and very little of the former, and crew casting will drive the budget and schedule rather directly.
Lock Locations, Build Sets, Get Props
You need to finalize your locations both for the budget and schedule (getting the final budget and schedule right is the driver for much of late prepro / early production), and so that your art department can start translating the Production Designer's vision into reality by building and buying sets and props based on the images and measurements gathered during location scouting.
You may not be able to build full sets for some locations (be it extensions and dressing for what is properly called a location, or a what is properly called a set to be used on a soundstage) at this point, because they're too large and/or site specific to be built in a workshop, but everything else is fair game. You want all the props and as many of the set pieces as possible to be done before you go on-set / on-location.
Finally, you need to just stop getting ready at some point.
There is a saying in the business: no project is ever finished, it merely gets released. (And many variations thereupon.) Script revisions, storyboards, production design, previz and camera test tweaks need to end some time, and probably some time before you spend more on them than you should have is a good time to do that (especially if you're observing diminishing returns in terms of making the storytelling -- visual and textual -- better).
You really need to stop changing these things as soon as possible so that all the rest of this stuff can get locked down -- especially the schedule and budget.
Movies usually go over budget and off schedule because of ongoing changes. Indecision, second guessing, infighting amongst power players, and so on can be the cause of these changes, but if they're not curtailed it can mean financial (and artistic) disaster.
Some studios, like Pixar, have spent years (and huge amounts of money) figuring out how to carefully balance the need for ongoing and sometimes very late changes to make the film better with knowing what not to change, and fitting those changes into a carefully crafted whole. Pixar has a well developed system for doing this, and a large, talented staff who have learned over many years how to pull it off. This approach provides great results for a few studios, and is an unmitigated disaster for others. And even for the experts, it is neither easy nor cheap.
The kinds of changes that require a lot of care (and cash) to pull-off aren't on-set moments of inspiration that take a single scene or a sequence in a slightly new direction, they're the ones that lead to big structural changes. You need to go on-set prepared to deal with little flashes of inspiration, big changes, and a million disasters of varying sizes alike by having a well-laid foundation you're building on.
If you go on-set with everything still in flux (or so recently having been finalized that you haven't had time to internalize your own vision and decisions), you'll get confused knowing what piece goes where, and things can easily spiral out of control.
If you find yourself continually making major changes throughout late prepro / early production, maybe your film isn't really ready for production. And if your film isn't actually ready for production, why is it in production in the first place? If more executives (and producers, directors, etc.) asked themselves this question seriously (paying it lip service is easy), there would be more quality films coming in on-time and on-budget.