Being prepared
If you have already read FIT, you know that voiceover jobs (or "narrator" jobs, as they're known in Japan) can pop up suddenly -- and you need to be prepared.
I have been given scripts for things ranging from processing pork meat to chemical research. I am not an expert in these fields (nor do I want to be); however, one thing I make sure I do (and you're ahead of the game if you've read FIT) is to come to the recording session prepared. Meaning: I know how to pronounce the technical words in the script.
There are a number of online sites to help you do that. Here are two that I've found helpful:
For daily English vocabulary: Merriam Webster.
For technical words: howjsay.
Both sites include online pronunciations so you can hear how to say any of those pesky, troublesome words. Do not assume there will be a producer at the session who will say the words for you; there might be, but don't chance it. Be prepared before you show up at the studio, and you will be the one they call next time.
(I chose the picture of my goldfish today because "clarity" is the key word for your recording session -- and they're beautiful!)