Does it bother you when you see tiles that are split to fit around pipes, valves and spouts? It should. Split tiles look pretty shabby, especially since cutting a hole in tile is neither difficult nor expensive. The easiest and neatest method is to buy a 1-1/4 in. ceramic-tile hole saw (from about $10 for individual bits to about $50 for kits). It has carbide grit embedded in the rim that allows it to cut into vitreous tile. The 1-1/4 in. size will work for most applications, but measure your valves to make sure. When using this saw, keep the tile wet and the drill speed low.
For more size flexibility, take the low-tech route of a masonry bit and a coping saw with a ceramic tile blade (available at a home center). First, drill a starter hole with the masonry bit. Next, detach one end of the coping saw blade, feed it through the starter hole, reattach it and go to work. Although it's slower, the advantage of the low-tech method is that you can make any size hole without buying more tools.
Video: How to Cut a Hole in Porcelain Tile
If you are tiling a bathroom, you are sure to run into a pipe or two you have to cut holes for. The Family Handyman editor, Jeff Gorton, shows you how to layout the hole and how to cut it with a Brutus hole saw kit for a perfect fit.