THE HIDDEN MEASUREMENT POP-UP MENU

You probably already know the trick about entering values in measurement fields in the Options Bar. You can change your unit of measure by typing the appropriate abbreviation after the value (for example, if you want 100 pixels, you'd type in "100 px"). But there's an even easier way (and you don't have to memorize a bunch of abbreviations). Just type your number, Control-click (PC: Right-click) in the field, and a pop-up menu of measurement units will appear. Just choose the one you want and it'll take care of the rest.