I always forget how to do this because I toggle this rather sporadically so I’m adding it to the public record.
To show hidden files in Finder pop open your terminal and type the text shown in the screen grab below.

To go back to hiding files we obviously just flip the AppleShowAllFiles flag to FALSE.

*Update*
As noted in the comments its nice to have the text available for easy copy and paste into your terminal.
Show:
defaults write com.apple.finder AppleShowAllFiles TRUE
killall Finder
Hide:
defaults write com.apple.finder AppleShowAllFiles FALSE
killall Finder
Thanks for the tip, I was trying to locate a hidden .cfg file for a particular application and I couldn’t use it anymore due to conflicting settings but that command line revealed the .cfg file so now I can manually change the settings, thanks!
Awesome! thanks.
Although it would have been much easier if there was a simple tick box in the finder preferences, like there is in windows explorer.
[...] to quickly access my .vimrc and other dot files using Finder. I found a couple of posts online (here and here) that described setting a property through the command line like [...]
This was the clearest, therefore the easiest instruction on how to get my system back to “normal”! I don’t even know why the .DS_Store files started showing up everywhere… but this really was so simple. Thanks a ton!
[...] the OSInstall file in the directory path specified. The terminal commands can be found here: Mac OS X – Show / Hide Hidden Files in Finder | Brooks Andrus I should get my 10V on Monday, so I'll try using EASEUS to shrink the existing XP partition, leave [...]
Thanks,
After following your instruction I was able to locate two +100Gb files generated by iMovie that filled my HardDisk [OSX Trash] and made impossible to operate with my computer.
Now I have recovered more than 200Gb space and my system is working fine!!!