I usually start from the inside, tape the top of the window, go up over the top of the door frame, come back down and tape the outside of the window. I do this two times on each side of the window close to the corners. You can drive around like this, if you have to. Also, to avoid scratching the window, I cover the inside of window completely with masking tape (easy to remove). That is just enough to protect the window. It works for me.