Ergonomics of the windows 8 app bar
An important thing to take into considerations is ergonomics. With Windows 8 and 8.1 came a lot of different devices, small 7” tablets, laptops, very large screens etc.
You need to think how people handle their devices, and with tablets you need to think about the orientation of the device as well.
Windows 8 apps is first and foremost made for touch, if you design with that in mind you will automatically get mouse, pen and keyboard to work too.
This picture shows you where the best, better and not so good areas are when it comes to reach. Because we think touch first, we need to imagine the user holding a tablet/slate/surface (whatever you prefer ;) )
Also keep in mind that most people are right handed.
So all important touch areas should be in the white area.
When it comes to text you should avoid those areas and put all important text in the top of the screen, that’s the optimal placement for reading and where your hands won’t be in the way either.