Slides are best understood when they are limited to a maximum of six text items as phrases or bullet points. Any more causes the text to become too small or presents too many points for the audience to keep in mind. More than five or six points should be grouped or chunked into subtopics, and then further information can be presented on its own side. Slides should include plenty of white space to avoid clutter. Material should not extend from edge to edge.
People read faster and comprehend better when there are margins around material.
While people prefer to read dark text on a light background, light text and dark backgrounds are also acceptable. The contrast must be sufficient. One of the most basic elements to consider is the structure of text. Text should flow from left to right and down from the top. When adding moving text to a slide, place text so that it moves from the right to the left, because viewers are accustomed to reading from left to right.