Most articles that deal with Production Sound Recording for video/film tend to cover microphones and recording/mixing techniques. I am not going to cover audio from the Sound Mixer's perspective, but rather from the contributions of other Departments. Why should other Departments care about improving audio? After all, except for Editing, the sound is not their responsibility, right?
Well, it is kind of like being on a naval warship. If anyone messes up and the ship takes a serious hit, then everyone goes down! Filmmaking is very much like that. Even though you may have done a great job in your Department, and contributed heavily towards one aspect of the film -- if one major area of the overall production quality is poor, and the film fails to be accepted for festivals or distribution -- then all of your efforts will remain a secret! On the other hand, if a film that you worked on garners awards and praise -- then having it on your resume is bound to help your career!
Bad audio will certainly sink an otherwise good film!
That being said, let's look at how other Departments can help the Sound Department improve the quality of the recorded dialogue.
Set construction for filmmaking is different than general contracting. Whereas the Zoning Board insists on 90 degree angles and perfect verticals, the law of acoustics prefer things to be several degrees off from perfect. Walls in a set should never join at exactly ninety degrees, but should extend outward so that sound waves (echo) reflect away from the set. Avoid parallel (wall) surfaces so that sound waves do not careen back and forth.
Allow the walls to tilt a few degrees from perfect vertical. This will also reduce room reverb & echo.
The camera lens will never reveal that your set is a trapezoid rather than a perfect rectangle. The slight variance of angle appears on screen as linear perspective (and NOT bad carpentry).
Do not use hard drywall to construct walls and flats. Instead, use a more absorbent media, such as "sound deadening board" which is like a compressed cardboard and sucks echo like a sponge. If the original construction was hard wood or drywall, then consider covering it with a thin layer of upholstery foam, deadening board, carpet padding, or something soft -- and then staple gun some fabric over it all for visual finishing. You can paint over the fabric, if needed.
Wherever possible, put some carpet on the floor to eliminate footsteps and reduce echo. I once worked on a show that had scenes in a Marines barracks. The image of a platoon of soldiers running about on plush carpet just wouldn't be realistic; but nothing in the rulebook said that the carpet couldn't LOOK like hardwood flooring! We used a fairly flat indoor/outdoor carpet and the set painters worked their magic to add the illusion of plank lines, nail holes, etc. The Sound Dept got their "carpet" and the Production Design got their "hardwood floor!"
Plan ahead for boom shadows on walls. A plain wall will turn into a projection screen of body shadows and boom shadows if left naked. Set Design should add textures to the walls, wall fixtures or decor, and create natural patterns of light & dark to hide or mask production shadows. The shadows will still be on the wall, but the audience should not be able to quickly discern and identify them as having been created by the filmmakers.
Furniture placement is another key factor. Couches and chairs should never be too close to a wall, or else shadows are a certainty. Move the actors (and their seating) towards the center of the set, so that the lighting on them can be barndoored so as to "bury" the shadow line of the barndoors where the wall and floor meet. Any shadows cast by the actors heads or the boompoles will not show up on the background wall. Use a separate "background light" to illuminate the wall, maybe even adding a cukaloris to create some patterns. If the actors were positioned too close to the walls, then there would be no way to separate their lighting from that hitting the wall behind them!
If the actors do have to perform close to a wall, then the sound dept has to be careful not to reveal the boom shadow (or to use alternative miking such as lavaliers or planted mics). This is where it is valuable to have fixtures, patterns, and textures on the wall to help hide the shadows.
Tables and desktops should be covered with a soft padding and then draped with a tablecloth of some sort. This reduces audio reflections up from the hard surface, as well as eliminates the clinking and clanking of items being manipulated.
Chairs that are out in the open may be difficult to reach with a boom mic if all the rest of the action is somewhere else in the room. Establishing a side table, ottoman, or magazine stand can come in very handy later on. It can provide a convenient place to hide a mic or even a light; not to mention blocking the frame in order to hide the presence of a power or audio cable. Ditto with tall plants, coat racks, and other furnishings.
Wardrobe plays a major role in sound recording. Choice of fabric and style will affect the use of body worn lavalier mics, be they hard-wired or wire-less. There are two types of clothing noise: acoustic and contact.
Acoustic clothing noise is created when the clothing elements themselves rub against each other and generate noise from friction or fabric crunching. Natural fibers, such as wool and cotton, are quieter than synthetic fibers. Starch may look neat, but is noisy. Use as little as possible, and only in strategic places where it is necessary, such as collars, center strips (where the buttons are), and shirt pockets. Excess starch can be neutralized by a puff of water from a plant spritzer.
Excess jewelry should be avoided, or at least replaced by plastic or rubber look-alikes.
Contact clothing noise is when the wardrobe physically rubs against the microphone head or leading several inches of cable. Reduce this noise by immobilizing any clothing on either side of the mic placement. Usually we accomplish this by means of a wad (actually a neatly formed triangle) of cloth camera tape, sticky side out, as well as with safety pins. Misting the area around the mic (see above) helps soften the starch and clothing fibers.
Often, the Sound Dept can prevail upon Wardrobe to create special hidden pockets for concealing the wireless mic bodypacks, especially when the same costumes are worn repeatedly. Sometimes they will also make special button holes or access points for threading lavaliers through outer layers of clothing (such as winter coats, suit jackets, etc.)
For example, a lavalier can be rigged through a small opening behind the chest pocket of a suitcoat or a labcoat and then "hidden" in the top of a prop "pen" that innocently protrudes from that same pocket.
If talent is scantily clad, then the Make-Up Dept may be called in to help. Mics can be hidden in the hair or beard. Or under a wig. Lavaliers sequestered inside a bra or halter top still have to "wired" down to the hip or lower. Usually, we just run the cable to the far side of the body, least likely to be on camera, and then tape the wire down using a clear, medical tape. Make-up is then applied over the strip of tape to blend it in nicely with the exposed torso. This suffices well for long shots; in a close-up where the skin would be fully revealed, it would be a tight enough frame to use the boom mic instead of the lavalier!