For Free-body-diagrams draw only the forces acting on the object in question.
Forces: 7 Newton's First Law:
For onjects at rest or moving at constant velocity the net force is zero.
Forces: 8 Newton's Second Law:
A net unbalanced force produces acceleration.
The normal force and the gravitational force are not an action-reaction pair.
Static friction exists between two surfaces when motion is impending; kinetic friction occurs when two surfaces are in relative motion. In either case, the friction forces are proportional to the normal force.
For inclined planes, the minimum coefficient of static friction u=tan 0