What surfaces do you have now?
They make a paint for this. Ask Lowes.
What are they made of?
You may need to add green board to your walls with this project. As per the first response, check with your local big box home improvement stores
Green board is not waterproof, only water resistant. Only recommended for the room walls not in wet areas,such as Showers. Should only use concrete board. Green board starts to break down in 5 years.
Hi JoAnn, here is a video that I found that is really good for waterproofing drywall behind shower walls.
You could put silicone on them
You have to water proof prior to tiling.