To show hidden files and folders on Mac OS:

• Open terminal
• Run following command:
  defaults write com.apple.Finder AppleShowAllFiles YES
• Relaunch Finder
  Press Alt + Right Click on Finder icon > Relaunch

To stop showing hidden files and folders:

• Open terminal
• Run following command:
  defaults write com.apple.Finder AppleShowAllFiles NO
• Relaunch Finder
  Press Alt + Right Click on Finder icon > Relaunch

Mac OS X 10.8 (Mountain Lion)