The most important part of tiling a bathroom floor is "setting the layout". It's a do-it-yourself job that anyone with a bit of patience and basic know-how can do. The key, says This Old House, is starting at the focal point of your bathroom for a nice, straight line.
Unfinished walls are a bit forgiving when setting tile, so try to line up your tile with something like a bathtub. Your eye will be drawn to that area, so you want to make sure the tile is straight and even on that edge.
Begin by taking equidistant measurements from each side wall and snap a line using a chalk line about a foot off the tub. This line will serve as the starting point for tiling the entire bathroom. Check out the video above to see an explanation of this in action, along with the rest of the grouting and tiling process.
How to Tile a Bathroom Floor [This Old House]