First clean the table thoroughly. Modern Varnishes are quite excellent and come in a variety of tints and finishes. Choose matt, semi-gloss or full gloss depending on the look you want to achieve.
In a well ventilated area, set your table on some bricks or wooden blocks (easier to do the feet and they won’t get stuck to the floor)
Following the instructions on the tin, apply the varnish thinly, working from the top down. Use a good quality well worn in brush with no loose bristles. Allow 12 hours to dry. it is important to ensure the first coat is fully dry before rubbing down with wire wool and then wiping down with a very slightly damp cloth before applying subsequent coats. The reason it is important to rub down after varnishing is that as the varnish dries, it will trap dust on the surface. If you dont remove the dust before applying the next coat of varnish it will become permanently sealed in to the finish. Three layers of dust actually cut out about 30% of the light which would otherwise go through to the grain and bounce back through the varnish. With all that dust in the varnish you will only ever end up will a dull, lifeless finish to your table.
The top of the table will need 3 or 4 coats to protect it, while the legs will be fine with 2 or 3.
If you are working outside, beware of pollen or airbourne grit landing on the wet varnish and ruining the finish. If working in a dusty garage, give it a good vacuuming and then damp down the floor to supress dust from rising as you work.