Establishing a Square Grid Pattern
We'll describe how to lay tile in a square grid pattern by dividing a floor of a basic 4-wall room into four quadrants.
First, snap chalklines between center points of opposite walls. Check the intersection with a framing square to make sure the lines cross to form 90° angles.
Lay tiles along the first quadrant guidelines all the way to the wall (alternating colors). If including a border, determine its width and snap a guideline around the floor's perimeter so the border tiles will look uniform.
Lay tiles square with the lines, working diagonally across each quadrant. Starting from the center point and working back toward the walls, laying the tiles in horizontal rows (1 green, then 2 red, then 3 green, etc.).
Check that the tiles lay out correctly then gather them up. Peel the backing off and press tiles into position, checking that they're square with the guidelines and/or their neighbors.
Or, spread glue over a manageable area and lay each tile into position. Keep a couple clean rags on hand and wipe up any excess glue. Repeat the process for the other three quadrants.
Once all the tiles are laid, roll out any air bubbles or extra glue. For large rooms, a 100 lb. roller (rental item) will save a great deal of time over hand rolling. But a rolling pin works fine for small areas.
Fitting Last Row Tiles
Tiles rarely fit exactly the length or width of a room. Tiles in the last row usually need to be trimmed to fit. Thankfully, there's a simple method for cutting tiles to fit perfectly.
Lay a loose full tile (this is the tile we'll cut) directly on top of the last installed full tile in the row. Line up the edges and pattern lines.
Set another loose full tile (this tile acts as a template) on top of the first loose tile and slide it tight against the wall over the space that needs to be filled in. Make sure it lines up straight with the row.
A portion of the bottom tile will be exposed past the template's edge -- that's the piece we need. Use the edge as a guide and mark a pencil line on the first tile.
Remove the template tile and cut the marked portion off the full tile. Test-fit the piece to make sure it fits well then press/glue it in place.