This guidance, originally published for an audience of physics teachers is sound for any lecture or demonstration presentation. Advice is to prepare and rehearse the talk in advance, being sure to include both introduction and summary. Artwork and visual aids should be uncluttered, legible, and in focus. Long equations, detailed calculations, and a requirement for rapid mental mathematics should be avoided. Demonstration apparatus must be visible to all and thoroughly tested. The speaker's style and manner should project enthusiasm for the subject.