Before you get to it you should level the bathroom the kitchen and or the hallway walls.
Sealing plaster walls before tiling.
Don t use paint glue pva wall paper paste only use the primer recommended by the adhesive manufacturer of your chosen tile adhesive.
You didn t say what adhesive you are going to use but one thing that is absolutely definate do not use pva.
Seal the walls with a skim coat and let it dry thoroughly.
New plaster work should be fully dried before tiling work is commenced this drying time varies upon temperatures but can take up to 4 weeks before fully cured.
Sand with a medium grit sandpaper to create a uniform surface that s not too smooth.
Adhesive grout and tile 20kg max weight onto plaster.
Thoroughly vacuum the area and give the wall a once over with a damp sponge or cleaning cloth.
Also keep the walls you are about to tile free of moisture dust and grease.
He gave me a list of their recommendations and one of them was to always use waterproof pva diluted before tiling on new plaster.
This way the adhesive will stick properly and last in the long run if you are using a good product.
Pva is not suitable for tiling for various reasons and this has been debated many times here in the forum.
Also now it s been plastered you will be restricting yourself to a tile with a max weight of about 16 kg m2.
Otherwise a few complications might occur.
If you choose a heavier tile you will need to overboard with a backaboard.
If in doubt prime the walls is a general rule.
You want the tile adhesive to have something to grab onto.