Shading the Detail
Careful, smooth shading keeps the eyes looking bright and shiny. Keep your pencil sharp and use small, find movements to create a smooth texture. The dog's leathery nose gets smooth, even shading too. Use the eraser to work back into some areas too, to soften marks.
Keep it Lively In this example the construction lines are fully erased, though often parts of these are left in a sketch, as they add interest and variation. Remember this is a sketch, not a photorealist drawing - you want to keep the drawing fresh and energetic, so don't get too obsessed about detail.