My first step is to pre-read the manuscript. Any surprise reveals? Is there a bad guy hiding in plain sight? An Irish brogue mentioned for the first time on the last page? And also, is the manuscript ready, ie, not riddled with typos or grammatical errors? Every mistake in the manuscript costs me time in the booth, pausing over it and making a note of it. A few is fine - I’m probably the last editing comb going through it, but more than one per page is not fine.
If there are any names or unusual/made up words, words I don’t know how to pronounce, and some words that I think I know how to pronounce but I’m not 100%, I will be making a list, and researching them, and asking the author how the invented words should be said. There are many excellent resources and most narrators employ the same set of online sources; I like Cambridge Dictionary, because it compares both British English and US English. Where I’m Canadian, I’m always getting surprised when I get caught out with common words that are said differently in the US (“foyer”) and sound incredibly strange to me. Worse, there are regional differences in how words are pronounced in different parts of the States, and I must defer to the preference of the author (or publisher)
Languages and accents are a whole ‘nother level of research and preparation!
Characters, especially when they’re written well, have a voice that just comes out through my mouth. I trust that. The words that have been put in their mouths and the adjectives that describe them go a long way to creating a voice for them.
After preparation, I record the “first 15 minutes”, not necessarily 15 nor the first minutes, but a sample that represents the book.
After approval that I’m on the right track with tone, pacing, and the main characters’ voices, then work proceeds apace. I send the audio files off to my sound technician for things to happen to it that I don’t understand (sound is a complicated energy with its own language and there’s a reason people go to school for years to learn how to manipulate it), and this mastering makes it sound as good as it possibly can.
I always work on one book at a time, not switching between books (except for doing pickups).
After the book is complete, or as chapters are completed, it must be proof-listened to to catch any sound flaws, edits that may have slipped through, and more. Any of those “pick-ups” must be fixed (back to the booth!), repaired seamlessly in the audio file, and then a final file is submitted to go on sale.
After final checks, a quality control delay, and the fulfillment of the contract, the book is released for sale on Audible, iTunes, etc.