How to clear MacBook Air "System Data" without resetting?

How do clear out the System Data, at this point it is taking up almost 60 GB on my hard drive, and keeps growing. Everything I read half of this is just junk the system builds up. Most of it is uncritical for operating, but Apple in all it's glory has refused to come up with a way to clear this all out.

Anyone have any answers on how to do this with out reseting the computer and rebuilding from Time Machine?

[Re-Titled by Moderator]

Original Title: Macbook Air System Data...