What factors can effect the amount of friction between two objects?

The force of friction between two objects is the product of the normal force and the coefficient of friction. The normal force is the component of force that is perpendicular to the plane of friction. For example, if you are pushing on a block of wood on the floor with a force F at an angle of 30 degrees above the horizontal, then the normal force N = F sin 30. The coefficient of friction is specific to the two materials, in this example the block of wood and the floor. In addition, there is a static coefficient of friction (applicable to a stationary situation) and a kinetic coefficient of friction (applicable when the object is already moving).