Identify the object and the surface it is in contact with
Draw a free-body diagram
Find all forces perpendicular to the surface
Set the sum of perpendicular forces equal to zero if the object is not accelerating perpendicular to the surface
Use the equation (N = mg) for a horizontal surface with no other vertical forces
Add any extra downward forces to (mg) when they act on the object
Subtract any upward forces from (mg) when they act on the object
Use (N = mg costheta) for an object on an incline when no other perpendicular forces act
Include acceleration terms if the object is accelerating perpendicular to the surface
Solve for (N) from the force balance equation