Things You'll Need
Chalk snap line
Notched mortar trowel
Floor tiles (at least 12 inches across)
Score & snap tile cutter
Floor tiles are laid in a grid pattern that starts at the middle of a floor and builds toward the walls. This ensures that the cuts you make by the walls are consistent all around. If a room is badly out of square, which is common in older homes, then you will need to make some adjustment to that layout, or you could end up with tiles that look practically triangular at the walls. The smaller the tiles, the more obvious the angle will be, so use larger tiles. Adjusting your layout to ensure you have no small cuts by the walls will help hide the off-square shape of the room.
Snap two perpendicular lines over the middle of the floor with your chalk snap line so they intersect at the center and divide the floor into four squares. Set a square at the intersection to ensure they're perpendicular to each other.
Lay out two lines of tiles, without mortar, starting at the intersection and building toward the walls. Assess how much room will be left at the ends of the tiles near the walls. If any of the spaces are less than half a tile wide, then move the whole line of tiles toward the wall so there will be a full tile at one end and more than half a tile at the other. Check the spacing in all directions. Resnap your lines as needed.
Use a notched trowel to apply thin-set over the floor, covering a few square feet at the middle in one corner of the intersection of the two lines.
Lay the first large tile in the mortar at the intersection along the two lines. Press more tiles off the first, putting spacers between them. Build out from the middle of the floor to the perimeter, applying more mortar as needed and keeping it all straight on the lines. Cover the whole floor with tiles in a grid pattern. Stop when no more full tiles will fit by the walls.
Measure the remaining space between the end of one tile and the wall, taking two measurements, one from each corner of the tile. Use a wax pencil to mark that line across a full tile for cutting. Note: The line will be at an angle across the tile, but shouldn't be too noticeable since there will be more than half a tile before it.
Make the cut on a score and snap tile cutter, angling the tile on the cutter as needed to get the marked line straight under the blade. Lay the tile in the mortar with the cut side facing the wall. Repeat this step for each tile.
Let the tiles set for 12 hours. Remove the spacers.
Grout the floor by spreading the grout over the surface with a grout float, pressing it into the joints and scraping it off the surface. Wipe up the excess grout from the surface, using a damp sponge.
Wait the manufacturer-recommended time for the grout to harden. Apply grout sealer, using the applicator bottle it came in.
Wear eye protection when cutting tiles.