As a tiler and bathroom fitter I have to drill a lot of holes in tiles.
For ceramics, I use the arrow head ones to drill through the tile until it just brakes through the back of the tile, then switch to a masonry to drill the hole in the wall. Before you drill, put the drill bit on the mark, apply pressure and turn the chuck by hand a couple of revolutions, this will mark the tile and stop the bit from slipping, no ned for tape. This method works for a masonry drill bit too but they are still prone to wandering a little. Oh and never use hammer for obvious reasons.
For Porcelain, I have used the small diamond coated bits in the past, keep them wet and at slow revs, it’ll take a long time but you’ll get there. I have invested in Rubi dry drill bits that attach to my grinder, they make very light work of porcelain and are a dry system so everything isn’t wet through, theyre designed to run at 1400rpm. If you’ve got a lot of holes to drill in Porcs, you can get these from a GOOD tile merchant with an adapter for a std or sds drill but will be £25-30 for a 6 or 8mm.
Which ever method you use, don’t drill the tile joints, this can crack tiles and do push the wall plug right through the tile and into the wall behind, otherwise tightening the screw could crack the tile as the plug expands.
Hope this helps.