This document discusses principles for using audio/visual aids in presentations. It defines learning resources as inputs that help acquire knowledge through instruction or experience. Learning resources can be non-electric, like books, or electric, like computers. When using PowerPoint, presenters should maintain structure and connections to make their message memorable. Effective visual aids maintain audience interest, promote participation, and can be used at all stages of learning. Considerations for using aids include quality, appropriateness, audience, and facilities. Overhead projectors allow face-to-face contact but have disadvantages like small text. Proper techniques include focusing attention and highlighting key points.