- Read the words
- Read the punctuation
- Read between the lines.
The words only tell us what to say, the punctuation tells us how to say it. There should be a slight pause at the end of a sentence or when you encounter a comma. You might use a longer pause when you encounter a semicolon, colon or dash. If nothing else, pauses give you a chance to take a breath.
When you encounter quotation marks your tone of voice should indicate the change from narrative to quotation.
In normal speech we tend to use an upward inflection at the end of a sentence when we ask a question. So if you encounter a question mark you should inflect your voice in the same way (note: in some dialects of English an upward inflection is part of normal speech).
An exclamation mark is the most obvious indicator that emphasis should be applied but if you read between the lines and try to imagine how it should be said. Which parts should be louder or softer? How can your tone of voice replicate the tone of the piece you are reading?
When reading poetry you have to capture the rhythm of the poem but prose can have rhythms as well. Modulate your voice and avoid monotone. Your audience will appreciate it.