Mac OS can be very slow after being used for long time( e.g. 1 year).. Deep clean right now is not possible without paid software.
Most Mac OS cleaner apps doesn't really boost the performance as much as advertised. I have tried all sorts of existing apps in AppStore, the result wasn't promising.
So I come up with an idea of writing a shell script to do this.
I tried on my own 2 mac, Macbook Pro and Macbook Air, with both running Mac OS X 10.9.3.. Result seems to be exceeding my expectation: 7.5 GB spaces are cleaned, and the system response has been drastically boosted..
Copy the script to your disk. and execute "sh clean_my_mac.sh"