Answer:
Your question was a little vague, but here are the most common techniques for shading.
Hatching (parallel)
Cross-hatching
Contour hatching
Step-by-step explanation:
Hatching- This can be considered the most basic of all of the shading techniques. It involves creating groups or patterns of parallel lines. These lines don't have to be completely vertical or horizontal. They can also be slanted or follow any angle you'd like, as long as this direction is uniform throughout the area you are shading.
Cross-hatching: Cross Hatching is like taking parallel hatching to the next level. You create a first layer of parallel lines (in any direction) and a second layer of lines is drawn on top in a perpendicular or nearly perpendicular manner. This technique is probably the quickest of all due to the fact that you are able to create darker values faster than with the other techniques.
Contour hatching: This technique involves using lines that follow the curves or lines of the initial contour/outline drawing. When used correctly, contour hatching enhances volume and three-dimensionality in a very striking manner. With this method, it is important to be able to visualize the three-dimensionality and planes of whatever it is your drawing.