standups and voice-overs
Delivery - Voice-overs
Besides marking the operative words for emphasis, you also need to mark your breaths on the copy - where you're going to pause to take a breath.
Longer sentences are going to need a breath, usually taken where a comma appears in the script or where new information is introduced.
But don't be too obedient to punctuation and don't pause for a breath after every sentence. Look for other places within a sentence where you can pause for emphasis and also take a breath.
Similarly don't just pause at the end of a sentence. Look for other natural places - such as the operative words within a sentence - to pause.
Try to sound conversational when you talk - not like you're reading from a script or lecturing to someone. Tell the story, don't read it.
Think about how you would talk with a group of friends and tell a story to them - then adopt that tone when reading your script. Be as animated as you would telling a story to a friend. Stay in the story while you're reading it. Think about what you're saying.
When reading a list of things, vary the pitch and the rhythm of each element of the list to add emphasis and make the list interesting. Don't sound like you're just reading a list in a monotone.
Open your mouth wide - both laterally and vertically, like a singer. Your voice will be louder and richer if you do.
Don't close your mouth at the end of a sentence. When you're talking that will create a popping sound when you open your mouth again to say the first word in the next sentence.
Keep your chin parallel to the floor - don't look down as that affects the sound of your voice.
You might try frowning when you talk to add authority and credibility to your voice. If you frown you are more serious, and your voice subconsciously changes to a more serious tone, making you sound more credible.
Don't "throw away" the last sentence of your script by letting your voice trail off just because you're at the end of the script.