I think one of the ultimate tools in drawing is being able to see negative space. Negative space is the area that surrounds the object you are drawing. A lot of times the edge of your object and the negative space form shapes that are much easier to draw than the actual object you are drawing. By drawing that negative space you are left with a good rendition of the object you are actually trying to draw. Some adjustments might be necessary after your initial pass, but you’ll have a nicely placed object with more accurate proportions to work from. It’ll take some practice to see the negative space, but the more you think about it and practice it the sharper a tool it becomes for you to use.
Here is the video for the first negative space exercise.
Here are some other images that are already cropped into squares for you to practice. I recommend that beginners do the crow and rabbit last. You can also use your own images, just crop them into a square to make it easier!