Floor tile layout process?
Software would be nice, but setting up your room diagram is probably more work than just trying your layout in reality. Plus, there's no substitute for actually seeing it in place.

I usually do this: 


Lay a row of tiles down the center of the long axis of the room. Don't forget to space them as you intend to do with the final floor.
At key locations, run perpendicular rows of full tiles as far as they fit.
Fill in any other areas as needed to evaluate the layout. 
If problems appear, shift the original row half a tile, so that the edge of the row aligns with the room's centerline instead. Also shift lengthwise as needed to reduce narrow tiles.
Analyze the layout again, and shift further as needed.


Once you find a satisfactory layout, be sure to look at it from adjacent rooms. If all is good, mark the key axis locations on the subfloor, and take dimension notes as a backup.