When a stone with a net force of approximately 0 is on a level surface, the primary forces acting on it include the normal force from the ground and the gravitational force pulling it downward. Additionally, atmospheric pressure creates a buoyant force on the stone, contributing to the overall force balance. If the stone contains magnetic materials, magnetic forces could also act upon it. The discussion emphasizes the importance of considering all potential forces, including less obvious ones. Understanding these forces is crucial for a comprehensive analysis of the stone's equilibrium.