Answer: First, when you go through a script, think of different emotions the character might be feeling.
In this monologue: http://freedrama.net/protecto.html At first he is excited, then in the middle he is sad or worried. Then he starts to get excited again, but then at the end he is confused and disappointed. You'd want to reflect that in your voice and acting. Show each of those emotions for each part.
Next, look at each sentence. Pick out a word or two in each sentence that you'd want to put the most emphasis on. In the line "I've always dreamed of being a hero." You might pick "dreamed" or "hero" or both to the be the words you say a little more clearly or forcefully.
I hope this helps!