GET RIGHT TO THE FILE YOU WANT

If you've parked a folder full of files in the Dock, you don't have to open the folder to get to a particular file. Instead, just click-and-hold on the folder for a moment, and a pop-up menu of all the files in that folder will appear (that's not the trick). Once that menu is open, on your keyboard just press the first letter(s) of the file you want and that file is instantly highlightedall you have to do is press Return to open the file.