Help Disk cleanup - best method?

[Bulldog]

I have recently gotten the "low on space" warning. I uninstalled a bunch of apps that were cool to have but rarely used and took up a lot of space. I noticed though that old directories are still on my SD card (and internal storage too I think). What is the best way to SAFELY run a disk cleanup? Any "gotcha's" to watch out for? Is there an app that analyzes my directories and recommends those not needed bases on apps currently installed? Thanks.

 

[Tweaked Halo]

I tried defragging ...didn't help. The only thing that got rid of it for me was a hard reset.