The sound recordist on the first proper shoot I worked on said something that I did not understand at the time and have thought about since. He said that by the time he arrives, most of his job has already been decided by people who were not thinking about him.
He was right, and the point generalises to nearly every technical department.
Location choice is the biggest single factor
A room with soft surfaces, some furniture, curtains, carpet, and a door that closes is easy. A room with hard floors, bare walls, high ceilings and glass is difficult and there is nothing in a recordist's kit that fixes it.
Reverberation is the specific problem. Sound reflects off hard surfaces and arrives at the microphone slightly after the direct sound, and once it is in the recording it cannot be removed. Modern processing can reduce it somewhat and the results are still audibly processed.
When a location is scouted, someone should stand in it and clap, and listen to what happens. If the clap rings, the room rings, and every line of dialogue will ring.
Nobody does this because location scouting is generally done by people looking at how it photographs.
Time of day is a sound decision
The second thing that gets decided without reference to audio.
Traffic, aircraft, schools, building work, deliveries, church bells, the hourly noise of a city. All of these vary predictably through the day and all of them are in your recording if they are happening.
A location that is unusable at eleven in the morning may be fine at seven. That is a scheduling decision made in pre-production and it is worth an enormous amount.
The version of this that has cost me most: a flight path. A location under one is fine for eight minutes at a time and then unusable for ninety seconds, and the schedule has to absorb that. Discovering it on the day means losing a substantial fraction of the shooting time.
What the building is doing
Air conditioning, ventilation, refrigeration, lifts, fluorescent lighting ballast, computer fans.
Most of these can be turned off. Whether they can be turned off is a question to ask the person with the keys, in advance, not a question to raise at the start of a shooting day when the person who can do it has gone home.
Ventilation in particular. In offices and public buildings it is often on a central system that nobody on site controls, and finding that out in pre-production changes whether you use the location at all.
Refrigeration is the sneaky one. A fridge cycles on and off, so a take recorded during the off phase and a take recorded during the on phase will not cut together. Unplug it and put your keys inside so you remember to plug it back in.
Wardrobe is a sound department problem
This surprises people and it is entirely real.
Certain fabrics rustle audibly, particularly synthetic outerwear. A performer in a waterproof jacket is going to be a problem for any microphone placed on their body and a problem for a boom during movement.
Jewellery. Watches. Anything that clicks against a table.
Shoes on a hard floor, which is a wardrobe and a location decision jointly.
Raising this in a wardrobe conversation before the shoot costs nothing. Raising it while a performer is in costume and ready to work costs goodwill and time.
Blocking determines what is recordable
The way a scene is staged determines whether a boom can reach and whether a lavalier will work.
Two performers far apart, facing away from each other, moving, in a wide shot, is close to unrecordable with one boom. It can be done with radio microphones and multiple recorders, which is a resource decision made in advance.
A wide shot generally means the boom has to be further back, which means worse sound. This is a direct trade between image and audio and it is worth making consciously rather than discovering it.
Directors who have worked with good recordists tend to block scenes so that the important lines happen where a microphone can be close, and it does not compromise the staging as much as you would think.
The schedule item nobody includes
Room tone. Thirty to sixty seconds of the empty location recorded with everybody silent.
It is used throughout post to fill gaps, to smooth between takes, and to make edits invisible. Without it, every gap in the dialogue is digital silence, which is startling and immediately audible.
It takes a minute and it is the first thing dropped when the day is running late. Editors are still complaining about this in every production I have been near.
What good pre-production actually looks like
Someone from the sound side visits the locations, or at minimum sees video with audio from them.
The schedule reflects noise patterns at each location.
Building services have been discussed with whoever controls them.
Wardrobe has been asked about fabric and jewellery.
And the shot list has been read by someone thinking about where a microphone goes.
None of that costs money. All of it saves a great deal of it, and the productions that skip it pay in post, where fixing sound is expensive and only partially possible.