How to fix your drawings
This is a very simple yet effective way to fix a lot of the problems beginner and intermediate artists have. Using the grid lets you see if things are a bit off, if they don't align, if a side of the drawing is a bit longer, they distance from the center, the center line for a drawing, etc.
Just doing this will improve your drawings in a big way, it will also make you work faster since you make fewer mistakes and have less guess-work.
Give it a try, I'm sure you'll notice a big improvement quickly.