Show Hidden Files in OS X 10.7 (Lion) and OS X 10.8 (Mountain Lion)
After a long search I recently replaced my aging netbook. I ended up with one of the new 13″ MacBook Airs on which I dual-boot OS X (for firmware updates, Xcode for iOS development) and Linux Mint.
Attempting to access an older project with some hidden files I discovered I could not see them by default. I went into File -> Preferences..., no option. I went into View -> Show View Options, nothing there that helped. Turns out the solution is a bit more cumbersome.
What you need to do is open Terminal and type in:
defaults write com.apple.Finder AppleShowAllFiles YES
Make sure you restart Finder after for the change to take effect.