Identify the maximum force applied parallel to the surface just before the object starts moving
Measure the normal force acting on the object
Use the formula μs = Fmax / N
For an object on a horizontal surface, use N = mg
For an object on an inclined plane, use N = mg cos θ
Substitute the measured values into μs = Fmax / N
If using an incline, find the angle at which the object just begins to slide and use μs = tan θ