Sketch in the basic outline of the eye. Leave a little dip on the inner edge where the tear duct is.
Draw another line outside both the upper and lower lids for the edge of the eyelids. Add a line above the eye where the eyelid folds back and a few lines below the eye.
Draw in the iris, pupil, and a small highlight. You can put the highlight wherever you want in the eye but I like mine where it is crossing both the pupil and the iris.
Look at your overall drawing and make any adjustments to the shape before moving on to the detail and shading.
Within the iris, sketch in some short lines radiating out from the pupil. Shade in the eye, making sure to leave that highlight white.
Darken the pupil. It will be one of the darkest areas in your drawing.
Shade in the fold above the eye. Draw in a few lines for the eyebrow. Add a little bit of shading below the eyebrow and on the side.
Lightly shade in the shadow that the upper lid casts a slight shadow on the eye. Sketch in the tear duct in the inner corner.
The eye is a sphere so the outside gets a little bit of shading as the sides curve back.
Draw in the eyelashes on the upper and lower lids with a soft pencil. They come out at different directions and different lengths. Keep them a bit irregular.