I listed the sound department second because even though they are often ignored (until something goes wrong) and often considered inferior to the other departments, the sound department is actually one of the most important departments on set.
As a rule of thumb, when people don’t notice the sound in your movie (unless it’s one of those high-def surround sound super-high budget blockbusters), that means your sound guy did a great job!
Bad sound gets noticed and draws attention away from where it should be – the story!
I don’t want to get too much into the technical side here but you’re going to want external sound (a mic that is outside the camera – not the camera’s internal mic).
I have had a boom operator who does his own mixing. That has worked out really well for me.
I know other producers that only use one person for sound. The ideal would be at least two, but I’ve been very happy with how the sound has turned out on the projects I have produced.
I lucked out, though, because the guy I use for sound is wonderful and professional and I use him in everything I do, if he’s available.
Pick good sound guys. I have never met one that didn’t do his job in a very specific way. A lot of them have their own equipment, which helps. If they don’t have their own equipment, and you don’t know anyone you can borrow from, you can always rent.
Once your sound department finds out what kind of camera you are using, he will be able to let you know what he needs in terms of external mics that he doesn’t have that is most compatible with your camera.
I’ve rented sound equipment before and for one day it’s not that expensive and it’s definitely worth it. If the audio professionals that you’ve brought on to the project are good at what they do, you’ll be really happy you invested in this area of your production.
By the way, you don’t need sound for shooting music videos unless you intend to add a bit of dialogue from your shoot. The song will be the underlying sound, and that should be all that you need.