Do tile floors have transition joints at the entry to each room?
Typically, tile layout flows from one room to the next. It would be visually disruptive to have extra joints at each doorway. You'll want to establish a single reference line, along with a perpendicular line at an appropriate location, and work from those. 

If you exceed say 30 feet in length it may be prudent to install an expansion gap. You'll want to talk with your tile supplier about that. We don't know where you live, what your subfloor situation is, or what you're installing.