Step 1
Start out with a basic sketch of a circle. The square makes it easier to sketch the circle. Use an F or HB pencil.
Step 2
Sketch in the iris and the outer eye.
Step 3
Use a blending stump over the whole drawing to soften the lines.
Step 4
Use an eraser to erase the highlights in the eye and erase unneeded lines.
Step 5
Use a soft pencil to sketch in the iris and the dark lines. 4B graphite works great for this, however, 3B and 2B can work also.
Step 6
Go over the rough shading with a harder pencil. A F or HB pencil would work for this.
Step 7
Define the eye by blending in your shading. Use a 4B pencil for the dark shading. Use a 2H pencil to add in some light texture. Use a kneaded eraser to pick out some light spots in the eye here and there.
Step 8
Finish up the eye by shading in the eye lids using an H or HB pencil and blending in the background.