I generally just turn the chuck by hand with a bit of weight behind it until the bit is through the initial glaze, and then drill as normal. I don't recall ever having a problem.
Masking tape, center punches or any other way of making your starting point is no ****ing use when the drill bits look like this. please log in to view this image
I can't be the only person thinking that this whole thread is a gay euphemism? Re-read the thread but replace the word 'drill' with 'cock'.
Just you, anyway despite all the conflicting advise I drilled the holes in the tiles so you can now steer the thread in any way you so desire