Todor Nikolov writes:
Since I started my Youtube channel a lot of people started sending me their Blender models when they experience a problem. I saw a lot of models over the last year or so and most of them suffer from the same few problems.
So instead of answering the same question over and over, I made this video. It shows the most common problems, how you may be creating them and how to avoid them. I hope it is helpful!