When I did mine.....
I hooked the hose of my shop vac to the outlet, and stuck the hose in the oil filler hole to pressurize the crankcase. This blows the shavings OUT as you drill (works GREAT!!)
Most guys will actually use a tapered punch to poke a hole in the pan, and keep pushing it in until the hole is big enough to tap. Then grease that tap to help catch shavings (use the shop vacuum hose for pressure, too) This method works well as long as you don't poke a hole in you oil pump pick-up tube.
On mine, I hooked the hose up for pressure, then used a Unibit to drill the hole in the pan. I then welded my oil drainback fitting (a heater hose fitting) to a piece of 1.75" x 1.75" plate with a hole in it (A large washer would work, too). I centered the fitting/plate over the hole using a deep well socket, then welded the 1.75" sqaure plate to the pan. It took maybe 20 minutes total from start to finish.
.