How do I show hidden files on a mac?

First, open terminal (/Applications/Utilities)
Then type this text exactly as it appears:
defaults write com.apple.finder AppleShowAllFiles -bool true

Then hit enter. This command will show the 'hidden' files in Finder. For the changes to take place, you either need to log out, and back in, or relaunch Finder (Force quit finder from the Force quit window should work).

To hide the files back, go back into terminal and enter the following command:
defaults write com.apple.finder AppleShowAllFiles -bool false

Notice, all we change is the "true" to a "false." Once again, relogin, or relaunch Finder.