First things first, decide on what kind of eye you want to have. Here I have chosen a shojou-esque type of eye style, which Ifind the most appealing (hee). First (actually second), I draw the realitive position of the eye to the face by the position of the top eye lash/lid, whatever. Then I draw in the bottom and then the actual eye. Add in lighting and a pupil and voila, you have a pretty eye...

(If it isn't try again, =P )