The visuals used in your PowerPoint will emerge naturally out of your script. The visual elements may be used to reinforce and make memorable what you are saying, or they may serve to illustrate and demonstrate the information being communicated. There are at least three visual elements to consider:
First, the slide design itself. Microsoft includes a number of design templates with PowerPoint. While some of these are good, many of them take up valuable screen space with graphical elements totally unrelated to the slide. Moreover, the theme of the design may have nothing to do with the content being presented. If you use a design template make sure that it reinforces the overall theme of your presentation. Also, consider using a simple background rather than a design template. A plain background with framed text can be very effective.
The second visual element is the picture or clip art. In most situations, the clip art that comes with PowerPoint is going to give your presentation a cartoonish quality. If that's what you want, great! On the other hand, if your content calls for a more serious tone, use photographs. In fact, some of the photographs that are a part of PowerPoint may be quite good. Do not limit yourself to Microsoft's photographs, however. There are a number of places on the Web where you can find high quality photographs at little or no cost. Generally, photographs are going to be more interesting than clip art.
The third visual element is animation. In earlier versions of PowerPoint, animation was limited to the way in which text appeared or disappeared from the screen. Over time, however, animation in PowerPoint has become more sophisticated. For example, simple animation can be used to explain or illustrate how x-rays work, the route taken by explorers, or a time-line. Once an animation is added to a slide, you can adjust the speed, timing, repetitions,direction, etc. of the element you are animating. In addition, it is quite possible to have two or more animations occurring at the same time. Through the use of basic shapes and animation schemes, you should be able to create or envision effective illustrations of complex points.
A final note about animation. Using elaborate animation schemes for text is not very helpful. In fact, it can detract from the content and simply make file sizes larger than they need to be.