The most important text should be placed at the top and in the brightest color. Arrange the material in a pattern related to how people read. Leave a larger margin at the bottom. This allows for extra room in case there are heads, tables or chairs in the way of the projector. Use uppercase and lowercase letters.
All capital letters are less attractive and harder to read.
Change colors, type size and weight to distinguish different levels of importance. Proofread your visuals. And then have someone else proofread them for you. Use the text justification commands to align text. Text aligned with the tab keys or the space bar may appear aligned on your computer screen but will NOT be on your output.