darrenba

Hi guys, another newbie here.

I'm in the process of adding a shower room under my stairs and was wondering if there are any tips for tiling the underside of the staircase. Is there any particular adhesive I should use to stop the tiles from falling off as I'm putting them up? Or should I be supporting them in some way?
Should I also replace the current plasterboard with aquapanel or is there something I can waterproof the plasterboard with?