FREE. "How to Prepare Effective Overhead Projector Presentations." This guide shows you not only how to get the most out of your overhead projector, but also what accessories and supplies you'll need, and demonstrates how to use them effectively. It covers everything from selecting the right screen to using your overhead projector with transparencies and LCD panels. Contact: National Audio-Visual Supply, Attention: Free OHP Guide, Rt 121 E, PO Box 116, Grafton VT 05146-0116. Fax: 1 800 628-1329.