You should know your material well so you can speak to it easily. You should practice slowing down and speaking up if you are fast-talking mumbler. You should

You should know your material well so you can speak to it easily. You should practice slowing down and speaking up if you are fast-talking mumbler. You should not be memorizing your exact lines and intonation, unless you are an excellent actor (Which you aren't, because you are a developer). It's creepy and robotic, and people know you are lying when you are barking words someone else wrote for you, that you don't understand or believe yourself.