It’s not hard to notice that Right-Clicking (Control-Clicking) on an item in the Dock brings up a menu with the option to “show in Finder”, which essentially opens up the enclosing folder of that Application or File.

Less obviously, Command-Clicking on an icon in the Dock will do just the same. But it doesn't end there. Command clicking has a similar effect when clicking icons in other places.

For instance, in the title bar of any cocoa app, you will see the name and icon of the open file. Command-Clicking on the icon brings up a list of all the enclosing folders.

Another example that could save you hours of wasted time, is command clicking spotlight results. This one is especially useful, as the other option (clicking on show all, finding the result, right-clicking and selecting show in finder) takes a long while in comparison.