Varnishing a table is simple as long as you use the right varnish and follow the 'Ronseal Principle' i.e. Do exactly what it says on the tin.
You will need a mask, varnish, brush, sandpaper, sealant and a little bit of patience.
Depending on the finish you are looking for you can choose between a matt, ... semi-gloss or full gloss finish. Clean the table thoroughly. If there are any holes or scrapes in the table, fill them in with putty. Leave to dry and then sand the areas to a smooth finish. Place the table at a height. This will make it easier to varnish the legs without doing your back in. (Place the table on another table to use as a work surface). Varnish the table in an open area that is well ventilated. The fumes can be pretty toxic (even if they"re not). Apply the varnish following the instructions on the tin carefully. Once the varnish dries, you can then apply a sealant. This will help to preserve the table and make it more durable.
Happy Varnishing.