First thing to ask yourself…is the room well ventilated? If you only have a window for ventilation it may be worth installing an extractor fan. This will limit condensation in the room therefore helping to prevent mould and mildew from developing on your newly painted walls.
Job one will be to repair any damage, holes or cracks with a filler and leave to dry. Walls previously painted in a bathroom paint, silk or with any sheen, need rubbing down with a fine sandpaper first to ensure the new paint has something to adhere to.
Chances are, the walls need cleaning down too, especially if it’s a high traffic area that gets used multiple times a day. To do this, simply use a sugar soap solution and sponge to remove any dirt. Finally, wipe down the walls again with warm water to remove any traces of soap.
With each surface, bear in mind how much condensation, steam or water splashes are likely to come into contact. This will help you to decide what the appropriate choice for wall decoration will be.
All of the fixtures and fittings need covering up with dust sheets and masking off with tape. A fiddly job but worthwhile. You don’t want to be scraping paint off your tiles and taps for weeks afterwards!