OS X using lots of memory for no apparent reason I have about 2 GB or more memory that I don't know what its used for. When I restart my computer with no applications running, the used memory is 4 GB, and when I open browsers its over 7 GB used from 8 GB total.

I checked the Activity Monitor, nothing is using more memory than it should be. I am also using Memory Clean app but I don't get more free RAM.

How to solve this? …or even debug my memory usage?

MacBook Pro, late-2011, OS X 10.9 Mavericks, 8 GB RAM
There's nothing to solve here. You should learn about memory management. The OS will keep as much in memory as much it can even seemingly outdated data that might be needed again (think of undo actions, reopened browser tabs, etc.)

However, if really needed to free up some memory, you can use the purge command in a terminal window.