Use a hole saw unit that has a center drill bit that will make a pilot hole first before the coring saw starts to cut into the tile. The drill bit should protrude out from the coring unit to allow you to start a pilot hole before the outer cutting teeth reach the table surface.
Be sure that your drill is at a 90-degree angle to the surface where your hole is to be drilled. Once the pilot hole has been made, gently set the coring teeth onto the surface with just enough pressure to make an impression onto the surface.
Using sprits of water will help to keep the temperature at the drilling site cooler. Allow the coring bit to progress thru the tile surface with gentle pressure to assure a smooth cut.
You can add an umbrella hole Table Ring.