First, start out with these simple shapes: a circle, which will be the iris of the eye, and a parallelogram. The parallelogram should be slanted away from the center of the face and positioned according to where ever the pupil is desired to be. In this case, I will hae the pupil looking straight ahead.
It is good to start out light since this is just the outline of the eye. This allows darker details without having to worry about losing proportions.
With this outline, create the shape of the eye using slightly more pressure on your pencil. The grneric shape should flow along the parallelogram. However, remember to use organic lines for the shaping of the eye rather than the geometric lines for the outline.
Notice the pupil is also outlined and positioned along with some extra circles in the iris, which i\will stand as the highlight or the shine in the iris.
The Iris: to create the texture for the iris, you must use a radial pattern that is centered with the pupil. At this moment you can fill in the pupil black. Then with simple straight lines, fill in thie iris all around. It is not necessary to have all the lines reach the ends of the iris.
Also, draw in the upper and lower eyey lids that line along the top and bottom of the eye, as shown below.
The Eyelashes: to do the lashes, you can use quick, “flicking” motions on the paper, Try to keep these strokes slightly curved and uniform. Keep in mind that the upper lashes are usually longer and thicker than the lower lashes. Also, keep in mind the angles of the lashes as they move across the eye. In this case, as they move towards the center of the eyes, they woul appear to be going straight up while the lashes ont he right corner of the eye point to slightly to the right.
Now you can add in more value and shadow into the iris. Remember, this part of the eye is the color of the eye. Depending on what color you want, the value of the iris will vary. Using the same technique as you did before, add darker lines in a radial pattern. It is ok to let the lighter value show through some of the darker values. Also, notice how i added a shadow at the top of the iris. This is to let the highlights in the eyes stand out more.
The generic eye is pretty much complete. To add from, shade the corners of the eyes as shown below. Also, you can shade around the eye for shadows and value.
Check out a related post on How to draw Generic Lips.