I posted your last question first. Why? Because it's very difficult to discuss a something if you don't speak a common language. The "technical vocabulary" and associated techniques are one of the very first things you should learn. As with any other discipline - be it filmmaking, medicine, law, architecture, etc. - it can become quite complicated. As many on this forum know I was a working musician for 25+ years, switched over to music engineering/recording, and then sidestepped into audio post. Even with all of that experience behind me it was several months before I felt I had a solid grasp on the processes of audio post, and quite a bit longer before I felt I felt that I was truly competent.
This is not meant to discourage you. However, you do need to understand basic techniques and associated tech speak. At the very least you will understand what your sound team is doing and what they are conversing about, and you can intelligently exchange ideas with them.
You learn all of the techniques and technical jargon (yes, a very daunting task) and spend A LOT of time - much, much more than a professional or even a talented up-and-comer - getting your sound right. As a one-man-band audio post facility it takes me between 2 (two) and 10 (ten) hours per linear minute to do the audio post on a project. You'll have to spend 2 (two) or 3 (three) times that as you are a complete neophyte. The positive side is that no one hears your mistakes; at least until you release your project.
This goes along with technical knowledge, so here we go with some tech talk. The three most common types of microphones are Dynamic, Condenser and Ribbon. There are two types of condenser mics; Large Diaphragm Condenser (LDC) and Small Diaphragm Condenser (SDC). Small Diaphragm Condenser mics are most commonly used for production sound.
Now we get into Polar Patterns - Omni, Lobar, Cardioid (subcardioid, cardioid, supercardioid, hypercardioid) and Figure 8 (bi-directional).
Production sound uses SDC Lobar/shotgun & hypercardioid mics on boom poles, and omni & supercardioid lavs.
Feeling a bit overwhelmed? And we haven't even gotten to mixers, recorders and time code, much less audio post. That's the problem, you can't know everything, and that's why you need audio assistance from someone.
For a start on production sound basics you should read "The Location Sound Bible" by Ric Viers.
Of course you should hire a professional, or, at the very least, retain a talented up-and-comer. You are hiring knowledge, experience and equipment. If you don't want to expend the resources then you have to acquire the knowledge, experience and equipment yourself. The biggest problem is that, even if you spent months gaining knowledge and bought cheap prosumer gear, you will be directing and someone else will be running sound for you, so all of your efforts become moot.
Audio post is all about details and layers.
When beginning a project I put together my cue sheets for dialog, Foley and Sound Effects. The larger the project the more important this map/guideline becomes. On a feature project this can me take up to a week.
The first chore (at least for me) is to get the DX (dialog) tracks right. The DX edit is using dialog from the unused alternate takes, DX wilds and ADR (Automated Dialog Replacement) to fine tune the dialog between the characters. You can fix mumbled/unintelligible words, excessive noise, and the like. You can even change the "tone" of the dialog. As an example, in the project "Last Exit" the female character in the opening scene came across as a bit too strident and abrasive, so by using dialog from alt takes I was able to make her more worried and vulnerable.
You can start with "Dialogue Editing for Motion Pictures: A Guide to the Invisible Art" by John Purcell.
The next job (in my personal process) is to give each scene a sonic base, the ambient sound. I have assembled a library of ambient canvases to use - empty street, busy street, office, forest, meadow, restaurant, bedroom, etc., etc., etc. These are my sonic canvases for each scene on which I can "paint" all of the aural details.
Now comes Foley, performing all of the human-made sounds - footsteps, punches, cloth, props handling and the like; details, details, details! This process becomes especially important if you are using DX wilds or ADR.
Your reading assignment - "The Foley Grail: The Art of Performing Sound for Film, Games, and Animation" by Vanessa Theme Ament.
Sound effects is the next job on the list, which for me is completing the ambient atmosphere and then adding everything from doors to vehicles to phones to weapons to… You get the idea. I personally (budget permitting) go into the field to record my own sound effects; I get the rest from libraries.
Reading - "The Sound Effects Bible: How to Create and Record Hollywood Style Sound Effects" by Ric Viers.
After that I drop in & edit the score and source music.
Then we mix.
And that's just the process. You'll also need the proper equipment (mics, preamps, DAW, Foley props, etc.) and, of course, the knowledge and techniques.
Once again, this is not meant to discourage you but is a forewarning of what you are letting yourself in for if you decide to handle all of this yourself.
Here's a few more books to read:
Audio Postproduction for Film and Video - Jay Rose
Practical Art of Motion Picture Sound - David Yewdall
Audio-Vision - Michel Chion
Sound Design - David Sonnenschein
So that's where you start.
As IndieTalk and AcousticAl have pointed out it is preferable to retain someone to handle the chores for you; filmmaking is a team sport, after all.
That's it for now.
Peace,
Uncle Bob