How can I effectively buff polyurethane to achieve a smooth and glossy finish?

To effectively buff polyurethane for a smooth and glossy finish, start by sanding the surface with fine-grit sandpaper to remove any imperfections. Then, apply a thin coat of polyurethane and let it dry completely. Next, use a high-quality buffing pad or cloth with a polishing compound to buff the surface in circular motions until it becomes smooth and glossy. Repeat the process with additional coats of polyurethane if needed for desired results.