Give your client a chance to ask questions as you move through your business presentation. If you move too quickly, it's easy for your prospect to get overwhelmed and not leave with a thorough grasp of what you're offering and thus not purchase from you.
Practice will help you give a sales presentation with confidence. You should practice with your visual aids to find the best way to incorporate them; you can also do a trial run in front of your co-workers or friends and get feedback on things you can improve. Work on your gestures and facial expressions. You want to be animated but not overly so.