You can get some good specific grout cleaners which are specific for doing the job. I use the Moldex spray when refurbing some commercial places if they are not re-tiling everywhere and need the existing tiling spruced up. As Flameport says bleach is they key ingredient when cleaning grout but i...
The guys here are right you should never use ready mixed adhesive with anything larger than a 300x300mm tile. I always use an S1 class of adhesive on bathroom walls because it's a good all round solution. It is important though when using any cement based adhesives onto a gypsum plaster that the...