I've had my MBP since May 2010. I've never done any "clean up" what do you suggest?

I started doing some clean up on my dad's old dell desktop and it got me thinking that I could probably make my MBP run maybe just a little faster if I did some similar cleaning up.

I googled around but could only find some dated information. What do you guys do to your MBP to keep them running great?

The first thing I did was remove all unnecessary languages using Monolingual.