Eyes are the windows to the soul, so goes the old saying, and it's especially true in illustration.
Next, draw a curve for the eyelid, using the top of the circle as a rough guide. Erase the guideline . Then fill in the pupil with a very dark colour or black before adding light-reflections as highlights. I find that it gives more realism if the light reflections go across the pupil and the iris. Finally, add eyelashes, and sharpen up details.