With the short pitches that most Angel groups and Venture "dating" forums allow, you have to really focus your content and use time and space wisely. So remove the agenda from the pitch (everyone knows what kind of content you have, or should have), make sure that your slides look professional and the color of the text against the background can easily be seen in a light room. Powerpoint provides enough free templates.
Use the title on each slide to highlight a conclusion from your slide discussion (e.g., Market Size of $2 Billion rather than just Market). Keep the font size large.
And perhaps most importantly, at the very beginning, be sure to very clearly state in terms your grandparents would understand, what you do. Sometimes that is very easy, sometimes very difficult. But you must do it, otherwise the audience will spend most of the time trying to figure it out, rather than listening to you (see Part II).