When you want to spruce up a boring wall and you don't want to mess with wallpaper, you could either paint a mural, which is fun or stencil a graphical repeating print. I have never even attempted wallpaper, but I've heard the horror stories from my parents. I think I'd like to avoid all that.
As I was looking at stencils and seeing what others have done, I noticed that a lot of the finished walls looked amazing. And then I googled to see what the tricks were. That's when I discovered that the #1 wall stencil trick is to start at the top center of the wall. Besides using a level and "sticky stencils" this was the most referred to because it ensured that the center wall was perfectly straight. Also, as the top was drying, you can move to the left and to the right, alternating, to let each section dry completely.