How to draw eyes

There are several ways to draw eyes, but today I show you some eyeshapes I draw often.
Some people start by drawing the pupil, whereas I prefere to start with the upper eyelid, but that doesn't make much difference.
Basically, I start with a straight or slightly curved line for the upper eyelid. 

You can draw a line to connect the upper and the under eyelid.

Then I draw a curved line for the under eyelid and then the details (brow, eyelashes, circle for the iris etc.). Just try what is comfortable for you.

 If there is something wrong about one eye, you mostly will recognize after drawing in the pupil, so I normally do this step last. For example, the upper eyelid of the left eye curves more upwards than the other. But this is just a little difference, so I won't correct this.

Here are some eyeshapes I have drawn for several of my characters:

As you can see, an eye has following parts which you can draw very different: upper eyelid, under eyelid, eyelashes, crease, eyebrow, iris, pupil. 
Mostly, male characters don't have eyelashes because it makes them appear more female, but there are also mangaka who create female characters without lashes as well to give them a tough look. Also rounder, bigger eyes are often used for young or naive, childish characters who appear very cute.
Because there are so many ways to draw an eye different, I can't show you a tutorial. But that's the fun part: you have to experiment and create new shapes on your own.
There are only three rules to draw eyes:

1: Eyes don't have to be even, because in nature nothing is exact the same. Just make sure that they look alike.
2: Between the two eyes is the space of normally one eye.
3: Manga eyes don't have to look realistic. Just be creative and draw the perfect eyes for your character!