Pick a light direction
Define a base color
Add a shadow color
Add a highlight color
Shade the form using simple planes
Darken areas facing away from the light
Brighten areas facing the light
Keep shadows consistent across the sprite
Use a limited color palette
Add edge highlights where needed
Shade around curves to show volume
Use ambient occlusion in tight areas
Keep contrast readable at small sizes
Match shading style to the sprite’s art style
Test the sprite on different backgrounds
Refine the silhouette and shading together