Polyurethane is the standard but I like hardening oils over polyurethanes, personally. BLO or Rubio monocoat if you have the money and want it as-easy-as-possible. Don't finish while you have large holes as the liquid will accumulate and get gummy instead of soaking into the wood. So prep the surface like the other poster suggested. If you do use BLO or similar be careful with the rags afterwards, people have burned down their houses.
Lacquer isn't great for dining tables because of its sensitivity to water and scratches
