First of all draw a circle.
Now draw these lines it'll help you to locate the area to draw eyes, nose, ear and mouth.
Now start drawing Eren's face beneath the circle.
Now draw Eren's eyes and ears he has small and sharp eyes.
Now draw his nose and mouth. Draw his mouth at the end of the circle.
Now draw his neck beneath the face. Draw these two lines for his neck.
Now draw his hair as you can see in the picture above.
Now draw his clothes and rest of the body.