There are right and wrong ways to move your windows and for some reason people ALWAYS want to transport them incorrectly. The most important thing to understand about windows is that glass doesn't bend-- It breaks. With that in mind, first and foremost: NEVER CARRY YOUR WINDOW LIKE A PLATTER!
Never place your hands on opposite sides of the window! This inevitably leads to carrying the window like a platter.
Your hands should always be on top of the window.
Again, and most importantly: Never hold your window as if it were a platter (horizontally). Carrying it as a platter provides no support to the center and allows the window to flex which causes glass to break.
And that's all there is to it.