Kevin, if you want to do a really nice job, go on line or to a local stained glass shop and buy a glass hole cutter. They come in all sizes. Cut the porcelain surface first. Then as Notchcad said drill the hole. SLOWLY! If you can get at both sides, cut the porcelain on one side first, then drill the first small holes to locate the center on the other side. Then cut the porcelain on the other side.
It will turn out super clean.
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