Measure the wall where you wish to install the towel rail and place masking tape on the areas to be drilled. The tape will help the drill stay in place, keeping it from slipping on the tile glaze.
2. Drill Bit
Selecting the drill bit is an important step. You need to consider the hardness of the material you are drilling through. In many cases, a carbide drill bit will do the job. Hardware stores usually have "glass and ceramic spade bits" and "diamond" drill bits too. Our testing on normal spade bits highlighted they get very hot and do not last long. The diamond drill bit is probably the best for very hard tiles - although it requires a bit of skill to use.
Ensure you use the correct size drill bit for the anchor plugs you are installing. It is better to be half a millimetre less than more as you can always shave a bit off the anchor.
Make a pencil mark on the tape where you wish to drill. Place the drill bit on this mark and drill slowly into the ceramic tile. It is usually best to pick a point away from the edge of the tile or the grout line, as it is more likely you will shatter or chip a tile if drilling on its edge.
Do not drill too quickly, or you risk overheating the drill and removing too much of the tile from the drill site. And do not use the "hammer" setting on your drill or you risk shattering the tile. It can be helpful to spray a mist of water on the drill hole while drilling - this is essential for a diamond drill bit. For a diamond drill it is also helpful to start the hole with the drill bit at 45 degrees until it pierces the outer layer, then straighten the drill.
Push plastic screw anchors into each drilled hole to firmly secure the screws inside the tile, and keep the towel rail from slipping out once installed.
Line up the rail and screw directly into the rail's escutcheons evenly on each side, if you're installing a one-piece towel rail. Do not tighten down the screws until all screws have been inserted at least part way and the rail is balanced.
If installing a rail with brackets, screw each bracket into the wall, tightening them down securely. Look at the side of the towel rail's escutcheons for a small grub screw, and unscrew it until it clears the inside of the escutcheon.
Place the escutcheon over the bracket and use a screwdriver or supplied hex key to tighten down the small grub screw on the side. This will attach the escutcheons to the brackets. Leave the escutcheons slightly loose.
Insert the rail into one escutcheon at a time, tightening each one down completely once the rail is in place to hold it securely.
(If you would like to know how to choose a heated towel rail that's just right for your bathroom, read these Tips For Choosing A Heated Towel Rail.)