Plumb and square in an old house like ours is a rare find. And there are no gray areas, like almost plumb or almost square. That can make working with materials like wall tiles tricky.
I didn’t have the luxury to just start with the bottom row of wall tiles and keep going. The first row was the most critical one: the one that had to be perfectly level.
I took care of that first row during the floor tile installation to give it enough time to cure before I installed any other wall tiles above it. I marked a level line on the wall and aligned the top edge of the tiles with it. The grout line between the bottom edge of the tiles and the corner profile has slightly varying widths, but it is very hard to notice as it is almost at floor level.
It looks like I used full sized tiles along the vertical corners, which was not the case. I had marked a perfectly vertical line along the corners that was a little short of the tile width. This allowed me to cut a fraction of an inch off the tiles where needed to adjust for imperfections along the vertical corners.
All other tiles that got filled in between the bottom row and corners were a whole lot more straightforward to install. Your typical tile spacers made the job easy and assured that all grout lines remained plumb and level.
I had another waterproofing aspect that I needed to address, namely the shower valve and shower spout. These are two breaches in the waterproofing membrane plane that are worth paying attention to. This is fairly easy as there are various products out there to do just that job.
Typical products that seal around the shower valve have a round piece of waterproofing membrane with an integrated rubberized gasket that fits snugly onto the plaster ground. The seal is adhered to the already installed waterproofing membrane with thinset, thus minimizing the risk of leakage.
The same applies to the shower spout, except that it has a smaller gasket.