These tricks work when you have the Shift key pressed. Indeed, they become a trick only when you press the Shift key. And the trick is to draw perfect squares, circles and lines at a certain angle. So, remember Shift when you are drawing one of those.
Holding the Shift key while drawing a line helps you draw a line at perfect 45 degrees or perfect 90 degrees.
Holding the Shift key while drawing a circle using the ellipse tools helps you draw a perfect circle. No more struggling wondering if you got it right!
Give a try to other shapes like triangle, pentagon, hexagon and stars as well. You will be amazed.
Also, check out our complete list of MS Paint keyboard shortcuts.