Slide Master -> Edit Theme ->Fonts

Edit the Theme

Try it: Format the Title Slide

Select the Master Title Style

Go to the Slide Master tab

Select a Font

 

The Built-in Fonts format the Title style as well as the many levels of Text Box styles.

 

Keep in mind that you are asking your audience to look at the text on a screen way across the room.

 

Choose a font that is plain and easy to read.