One of the things that I notice about a room is the ceiling. Especially the way a ceiling grid is placed relative to the walls. I think that when the grid terminates against the wall with a tiny piece of tile it looks like shit. I wonder, "Did the architect cause that because of some other relationship that I can't see? Did the contractor just do it?"
My mentor taught me better. "No pieces less than a half tile - anywhere." I found that you can almost always do that. It might mean that you have to center the grid intersection in the room, or center a tile in the room, or start with a slightly offset grid. But there is always a solution. If you try.
There are special challenges - non-parallel walls, skewed walls, floating items like a section of wall or columns. CAD really simplifies things since you can move a grid around until you are happy with the edge conditions. Include fixtures in that exercise and kill two birds with one stone. Some times there might not be a great solution unless you can change the layout, which seems a bit excessive. Light fixtures complicate things. Occasionally you find that you can't place fixtures where you want and locate the grid ideally.
One way to minimize the issues is to use a planning grid of 2'x2' or 4'x4' when laying out the walls in the first place. If you stay on the grid, which is hard to do, you get a great ceiling tile layout automatically.
At some point we decided to write a recipe and move on to worrying about bigger issues. We called that recipe:
Rules of Ceiling Grid Placement
Rules 2 and 6 are key.
Rules 1 and 7 can be violated for good cause.
Rules 3, 4, and 5 can almost always be met.