Any information projected onto the screens is to be viewed by up to 400 people in a large auditorium.
What is very legible in a meeting room may not be suitable for use in the Sanctuary.
When preparing your presentation materials, be anxious that everyone in the audience can reasonably see your content you are projecting.
As a rule of thumb, if you are using PowerPoint, make sure that no text character is less than 40 "points" (PowerPoint terminology).
Put it in another way, if your whole screen is completely filled with text of the same size, the character size should be so large that the screen can only fit 10 or 11 lines. If you can fill more lines, your text size is too small
For an example, check out this sample file: 
FERC