Drawing a square

As you might have realized by watching the video, I'm not very good at drawing. However, with some tricks it is possible to draw a square (well sort of). Often, if I draw my squares without measuring, they are either too wide or too narrow. I guess practice makes perfect.

Another way of checking is to keep turning the drawing 90 degrees (a quarter of a full turn) and back in the same plane as the drawing, and visually inspect if all sides are equal in length. Alas, my current video setup doesn't allow me to take shots from above. I'm looking for a better video setup, but for now I settle for a tripod and placing a sketchbook vertically on a table against the wall.