Digital rendering and brushes for beginners

[darktiste]

You shadow side you need to hit your darker harder it common among begginer to be timid when dealing with there dark they go to soft on them.Also remember that your trying to give the illusion of roundness so there  is gradient that going to hapen on your form. Meaning that since the light is coming from the top right a bit from the side you get more light on the sphere where it facing use and the more it goes toward the side of the ball it get dark as it away from the light source.