Tip 24: Font size. It is only worth presenting slides if people are able to read them.
More specifically, people wearing glasses need to be able to read them from a decade-old projected screen in a sunny room from 30 feet away.
USE LARGE FONT.
Guy Kawasaki says font 30. I think your font size should be a mathematical function of the average age of your audience and the square footage of the room - but you get the idea.