When using Adobe Illustrator, drawing with stipple brushes can be a very effective method of shading. Of course, there are other methods of shading, such as using gradients or blends. But using stipple effects, will produce more of an organic look and feel to any graphic.
You can find free stipple brushes online but quite often it might be hard to find one to suit the project you’re working on.
So why not simply, create your own!