Very few scripts present the voice over artist with a phrase or sentence he or she hasn’t heard in real life, often many times. The voice over artist draws from that experience. Just because it sits there written on a page doesn’t mean that the thought process for delivering it should be any different from what you’ve experienced in real life.
An amazing number of people read aloud without knowing the meaning of what they are reading. Many read in a droning mode that elicits little or no effect on the listener. Moreover, many corporate CEOs and politicians have the ability to mesmerize an audience as they speak spontaneously, but the minute they begin to read from a script, some emotionally turn to stone by comparison.
It is absolutely vital that you fully understand the script before you deliver one word of it. If it is a particularly difficult, industry-specific, technical, or medical script, then at least try to get a general sense of it. If you know, for example, that the solution in beaker A must be poured into beaker B and then heated to form a thick, jellied solution, it doesn’t matter that sodium carbonate is in beaker A and phenolphthalein is in beaker B. You have a sense of what is going on in the process and can transmit that to the listener. Pronunciation of these terms can be picked up from the producer and notated phonetically.