I think theres a confusion between plumb and level here!
To work out cuts here is one method, it is quite simple
Measure from top to bottom of the wall and mark the middle. Place your chosen tile on the wall above the mark you have make for the middle and then make a mark at the top of the tile, don't forget to add how ever many mm you need for spacers. Repeat this up the wall. When you have reached the top check that the last full tile doesn't leave you either a sliver to remove from a full tile or a sliver to install. Depending on tile size and preference you should be looking for more than 1/3 of a tile rip IMO, preferably more than a half.
If the ceiling is not level or very wavy you need to have the last tile cut as large as possible.
If you measured correctly then the cut of tile you are left with up top will be the same as the cut down low, check it out. When you get to the mark of the bottom of the last full tile, that is your starting point, attach a batten to the wall making sure its perfectly level.
Problems -
First one you will want to deal with may be that you have a little sliver cut all along the top and bottom, if this is the case then adjust your starting point, a good tip is to go back to the middle mark and place the tile on the wall with the mark in the middle of the tile, this will obviously chance the rip size by half a tile and should sort your problem out.
Second one is that there will be a bath in the room and after marking put everything you have an awkward rip to make along the top of the bath, You will need to work out your starting point by either lowering or heightening your start point, don't forget that you'll need to check your top and bottom cuts again.
Other obstacles, fitter furniture and windows should all be taken into consideration, at times a complex room can have more time spent on it planning where to start than you'd expect, a nice job takes a bit of planning,
Do the same along the length of the wall to find out what rips youll have in the corners, never start a full tile from a corner, the wall wont be straight and if it's out be only one mm then it will show. If there is a window on a wall then you want to try and work from the center of that, there will be exceptions when this wont be able to work but it's rare in my experience.
