Begin with some cross-hairs. You'll want your Mickey to be proportional, so this is an important early step. Use a ruler for precision and faint pencil lines so that you can erase later.
Mickey is composed of a series of circles. This one will give you an idea of where the head should be. Additional circles will stem from this one. Use a protractor for perfect circles.
Grab your ruler again and draw lines to represent where the body will go: torso, legs, and arms.
It's just that simple!