One of the easiest ways to push your presentation to the next level is the proper use of typography. Your company has a brand, and probably a corporate typeface or two that the marketing department uses in your corporate collateral. They might even have the corporate typeface in both PC and Mac formats. Easily installed on your computer, using the corporate typefaces in your presentation is the best way to simply put you "on brand" without fear of offending your company's branding police.
You can find a very simple tutorial on installing new fonts on a PC using various Windows operating systems here. A similar tutorial on installing fonts on a Mac can also be found here.
In absence of a corporate type face, there are always alternatives to the lazy standard of Windows Arial, which is really a Microsoft-owned nearly identical rip-off of Helvetica. Using a clean, easy to read typeface is of utmost importance, but don't rely on the standard default font that PowerPoint force-feeds you. There is nothing memorable about a Windows operating system font on the wall.
Tomorrow, I'll provide a list of my favorite typography sources—free as well as pay-to-own. A simple type change can make a huge difference in the emotional connection of your audience to your visuals.