If you're going to get Google Chrome...

 You should try at least 4 extensions.

 

NUMBER 1:
If you have a Pandora Account, try out the Better Pandora to help block out ads and other annoyances
NUMBER 2:
YouTube Downloader, downloads any youtube vids as flv's or MP4's
NUMBER 3:

Google news, you'll find it somewhere. great way to keep up to date- especially if you need a current event for World Geography.
NUMBER 4:
Sometimes google news is not enough for cool people who are on the edge. Technology News works the same as Google News, just gives you some headlines and lets you pick what to read more of

As for themes, if you want to keep it together, just stay with the default, Classic Blue Chrome Theme. Anything else will get kind of distracting.
If you want some thing cooler, try Halo Reach themes, or Tiger or Midnight Tiger, or the series by www.electrodexs.net

-Retrotech