Review the script.
Every time you must use the keyboard to start an animation or transition, put a mark or word in the script so you will remember to do it as you read. (see example storyboard followed by script below)
Print a copy of the script
Practice, practice, practice
Practice speaking the script aloud without the presentation.
Put feeling and emotion in your voice where appropriate
Enunciate your words carefully.
Practice speaking the script aloud with the presentation including the builds and transitions.
Find a quiet spot to record the presentation
Be as quiet as possible when using the keyboard for animations and transitions. Otherwise that sound of the keyboard might be heard in your narration.
Listen/watch the presentation. The recording can be cleared if you want to record it again.
Don't forget to SAVE when you are done!