On the narration and audiobook sides of this business, we often encounter words whose meaning or pronunciation are unknown to us.
Get in the habit of looking up every word you encounter in a new script, whose meaning you do not fully understand, and look up its meaning in a good dictionary, as well as its correct pronunciation. Study and learn the phonetic spellings in the dictionary and how to use them to pronounce the new words you encounter. Bookstores offer vocabulary builders of many kinds that you can use to learn 15 to 20 new words per week.
If you specialize in medical, technical, or IT scripts, it would be a smart move to buy an appropriate dictionary for any/one of those categories, as the necessity for looking up definitions and pronunciations of new words occurs far more often in these areas than in the average script.
With these approaches, your vocabulary will grow steadily, and poring over a new script will go much more efficiently.