Question: How can I change the default font for a new PowerPoint presentation
Answer: You can go to the slide master (View ribbon tab) and change your theme or fonts there. If you want the same font throughout all slide types of your template, the easiest way is to select Fonts from the background category and select a font combination. These will be applied to all types of slides in this template. Otherwise if you want specific types of slides modified, you will need to select the style from the left panel. Then close the slide master.
Note: If you would like one of the UNMC templates as your default style, you can find one at http://info.unmc.edu/branding.htm and scroll to the PowerPoint templates.
THEN….The most important step then is to save it as a “blank” template in this folder C:\Users\UserName\AppData\Roaming\Microsoft\Templates (user name would be your name). By default, in Office 2013 if you change the type to .potx, you may not be in this folder. In 2010, it should be the correct location. So you may have to search for it. After saving, verify by closing PowerPoint and restarting and select “Blank” (2010) or ”Default” (2013) theme.