Here's how you can download a free tool called Lion Tweaks 2.0 to customize OS X Mountain Lion.
1. Go to the Lion Tweaks 2.0 download page.
2. Click on the Free button.
3. The software is free, but donations are accepted by the developer.
Here's a list of what you can do with Lion Tweaks 2.0:
Show/Hide the user Library folder.
Change to a 2D or 3D dock.
Enable/Disable system window animation.
Enable/Disable mail reply animation.
Remove/Add Reading List Icon in Safari.
Enable/Disable Spelling Correction.
Enable/Disable repeating keys.
Enable/Disable permanent scrollbars.
Show Hidden Files.
Disable Crash Dialog Pop-Up.
Get a new Stack List View.
Highlight Stack items on mouseover.
Change iCal leather interface to aluminium
Change Address Book leather interface to aluminium
Disable resume for a single app
Enable the hidden FTP-server
Customize Launchpad folder background
Disable local Time Machine Backups
Enable Airdrop on old hardware
Enable colours in the Finder sidebar
Enable iTunes Dock Animation
Enable TRIM support in Lion
Enable secret iCal debug-menu
Remove Spotlight icon