Mould will grow in a moist environment, and showers are wet.
Any areas where water pools should be eliminated. Dehumidifiers (e.g. ventilation fans) are good, but they only help by removing and possibly circulating the air (i.e. exhausting existing air results in drier air from elsewhere in the house replacing it in the shower room, thus reducing humidity).
The main problem with moisture occurs due to condensation. This happens when water is present in the air, and it condenses due to a temperature decrease (warm air holds more water than cold air). Hence, no amount of exhaust ventilation will result in all water evaporating. In my shower room, for example, when it's cold, water condenses on the window and walls, then droplets merge and it dribbles down the wall collecting more water as it goes. It also condenses on the ceiling, which unfortunately happens to have an outside air vent above it in the attic.
One solution to this is to heat the air in the room (warm air absorbs more moisture, which can then be evacuated with an exhaust fan). Warming the shower room before having a shower will prevent some condensation, as the walls and ceiling of the room will be warmer, and thus less likely to cause the air in contact with it to cool and thus water to condense.
I'm planning on installing the Panasonic FV-11VHL2, but any means of heating (e.g. having the heater/HVAC on) and evacuating (exhaust fan) should do the trick.
A couple of other points (from experience):-
- Full panel glass shower doors don't have cavities inside which water can accumulate when caulk sealant deteriorates. Notice how for this shower door there is no track at the top or bottom. Such tracks are usually hollow and moisture can pool, attract mould and its spores, and potentially travel elsewhere via capillary action.
- Mix anti-mould mixture with paints before painting if they don't already contain it (something like Krud Kutter MC-2 Paint Mildewcide)
- Ensure that any caulks used have a Mildewcide in them. Research online the effectiveness of such caulks before buying. Over time, however, even the best caulks will have their effectiveness reduced. In this case, remove and recaulk.
- Seal tiles and grout periodically with a good sealant.
- Consider wiring the ceiling fan to a humidity-sensor timer, that allows timed operation (i.e. manually operated countdown time function), but also automatic activation if it senses the humidity level is too high.