Hi, don't use a hammer drill on a TILED WALL it will damage the tiles. I've just drill holes in a tiled wall in my bathroom, use a masonry drill bit and take your time, a 400rpm drill may take a bit longer, but so what the finish wil be the same, keeping your drill straight. It worked for me........
400 rpm might be a bit slow. Here's a tip. Stick a bit of clear tape over the spot you want to drill, it'll help centre the bit. Use a masonry drill, better still an arrowhead bit, and start slowly until the bit gets biting. Once your into the tile. through the ceramic face and into the tile body, you can switch to hammer action.