To show the hidden files execute the command below in a terminal window:
defaults read com.apple.finder AppleShowAllFiles -bool YES

To hide these files again execute the command:
defaults read com.apple.finder AppleShowAllFiles -bool NO

While Apple helpfully provided a keyboard shortcut for use in open and save dialogs, they didn’t do the same for normal Finder windows. Luckily, it’s not too tricky to set up a keyboard shortcut yourself.

To start, open up Automator (in the Applications folder) and choose a Service template. From the library choose “Run Shell Script” and drag it across to the workflow area. In the text box paste the following command:

STATUS=`defaults read com.apple.finder AppleShowAllFiles`
if [ $STATUS == YES ]; 
then
    defaults write com.apple.finder AppleShowAllFiles NO
else
    defaults write com.apple.finder AppleShowAllFiles YES
fi

Finally, change the “text” drop-down menu to “no input” and then save you workflow as “Toggle Hidden Files”.

Now if you go to the Finder menu and look under Services, you should find a “Toggle Hidden Files” option. To add the keyboard shortcut, go to the Keyboard section of System Preferences and click the Keyboard shortcuts tab. Select Services from the list on the left, then scroll down to the bottom of the list on the right to find “Toggle Hidden Files”. Double-click on the area to the right of it, then press the keyboard shortcut you want. I used Command-Shift-. (dot).