Avoid the temptation to present everything you know on a subject. One way to help your audience understand what you are saying is to use visuals. These can be slides, transparencies, or videos. The visuals should be simple and you must take time to explain them. For diagrams that means simple line drawings or computer images, legible labels, and a guided tour through the important aspects.
Few people feel comfortable speaking before an audience without something on paper.
However, do not stand up and read sentences that you've written down. In either case, make a note of the places in your talk where you plan to show a visual. Or use one card for each slide if your presentation follows a series of slides. One item you cannot neglect for a smooth and comfortable talk is practice. Practice, practice, practice.