How should I prepare the shower walls for tiling to prevent mold and mildew?
The main things you need to do are in other areas:


Make sure that the shower area is properly ventilated. Install a fan if necessary.
Make sure that as much of the water can drain away as possible.


You can seal the tiles after installation which will inhibit the growth of mold, but make sure that the grout is completely dry before application.

You can also use anti fungal cement and grout to inhibit the growth, but this would only have a minor effect.