Use a drill press if available. Start with a slight off-angle (very slight) in order to get a "notch" to catch the hole saw. Go at a steady slow pace. Tape the back side, or do something to support it to prevent chipping (similar to tearout in wood working.) When you are almost there, go extra, extra slow. Use plumbers putty and water. Check the water temperature- when it is warm, or when there is just too much funk in it, pour some new water in.
Good luck!
-A