It looks like Google has made a few recent changes in Gmail. And by changes, we really mean — added some new functionality. The latest deals with starring and labeling. More specifically, Gmail users can now Star and/or Label messages before they are sent which should help you to keep track of an email that you know (or think) you will need to follow-up with. The setup is simple, when composing said email you will simply need to choose the Labels drop down which will give access to your labels and the ability to Add Star.
Via [Official Gmail Blog]