Every great space saga ultimately comes down to the same question: light side or dark side? Usually, it's debated on a space station, with humming lightsabers and plenty of drama. In your home, the decision is far less spectacular—just one finger press right next to the door.
The light switch sticker divides your switch into two camps. One half light, one dark, each with its own lightsaber. Five by five centimeters of vinyl, bubble-free application, fits standard single switches.
Which orientation do you need? It depends entirely on your switch. If your light turns on when you press up, choose Light up, dark down. If the lower half switches on your light, choose Dark up, light down. Take a quick look first—otherwise, you'll end up switching on the lights with the dark side in the future, and that really makes no sense.
For everyone who wants to make a fundamental moral decision the moment they enter the hallway. The dark side saves electricity, by the way. ;)