How unique is your idea? The best way to show off the originality of your product is to present a working prototype of it. If a picture is worth a thousand words, a great prototype is worth a million. Your prototype should resemble the finished product as closely as possible. You may be able to look beyond that duct tape or bad paint job, but your audience won't.
If your idea is a service or is something intangible, such as software, show storyboards or make a computerized presentation. You can even present a well-drawn model of your idea as long as it easily communicates your concept. The quality of your prototype or rendering speaks volumes about you. It's your silent salesperson, telling prospects you're professional, detail-oriented and prepared.