1- First do an outline of a letter or a full piece.
2-Now think of where you want your light source to come from, pick an angle (remember shadows are the dark side of a light source)
PS you do not really have to draw the sun.....
3- Now that you picked the angle of your light source, pencil in the opposite sides of the angle that the light is hitting on the letter. And stick to the exact design of the letter when drawing the shadow.
4- Now you can ink in the outline of the shadow like this.
5- or you can color it in black or any other color you like.