To refinish a wooden table, sand the entire table by hand or with an orbital or belt sander. Apply at least two coats of varnish, then apply polyurethane to seal the stain into the wood.
First, sand the entire surface of the table, side edges and legs. This removes the previous varnish from the surface of the wood. If using an electronic or battery-powered sander, do not gouge the wood. Use 100-grit sandpaper for the initial sanding, then use 150-grit paper, and finish with 220-grit sandpaper to smooth the grain of the wood. Use a tack cloth to remove all sanding dust.
Apply the new varnish with a brush in the direction of the wood's natural grain. Apply stain liberally. Allow the varnish to soak into the wood for a few minutes, then wipe off any excess liquid. For a darker final result, allow the varnish to soak longer before wiping.
Apply at least two coats of stain, depending on desired color depth. Wood expands as it absorbs liquid varnish, so sand with 220-grit sandpaper, and clean with tack cloth between coats to smooth any swollen fibers. Allow the final coat of stain to dry thoroughly, and then apply at least four coats of polyurethane. Let the final coat of polyurethane dry for at least 24 hours before using the table.