How to effectively sand hardwood floors for a smooth and professional finish?

To effectively sand hardwood floors for a smooth and professional finish, start by using a drum sander with coarse sandpaper to remove old finish and imperfections. Then, switch to a finer grit sandpaper and use an edge sander for corners and edges. Finally, finish with a buffer and fine sandpaper for a smooth surface. Vacuum thoroughly between sanding stages and apply a sealant or finish for a professional look.