Have you ever been frustrated when trying to find a hidden file, or a file in a hidden directory, from an application’s open dialog? I’ve run into this a few times when trying to open disc images from disc utility. There’s an easy solution: browse to the directory where the hidden file/directory is, and hit:

Command-Shift-. [period]

This will show the hidden files. Hitting the same combination again hides them again. This might not work, depending on your region settings or key bindings. Try Command-Shift-, [comma] instead.