Sand the entire table removing all stain from edges and legs. If using an orbital or belt sander, be careful not to gouge the surface. Do most of the initial sanding and varnish removal with the 100-grit sandpaper, then step up to 150-grit and do a final pass with 220-grit to smooth out the grain for the new finish.
Carefully remove all sanding dust with a tack cloth.
Apply stain with a brush, following the wood's natural grain. Apply stain liberally, allow it to soak in for a few minutes then wipe off excess. Tip: The longer stain sits before wiping, the darker the final color will be.
Apply at least two coats of stain. Depending on the desired color depth and richness, apply more coats. Lightly sand with 220-grit paper and clean with tack cloth between coats. Note: Staining the wood causes the wood fibers to swell as they soak up the stain. The reason for sanding between coats is to knock down the swollen fibers to maintain a smooth surface.
After the final coat of stain has thoroughly dried, apply polyurethane according to the manufacturers' instructions. Apply at least four coats, since dining room tables get a lot of use. Allow the final coat of polyurethane to dry for at least 24 hours before using the table.How to Refinising a Dining Room Table