Measure each side of the room you're planning to tile. Divide these measurement in half and mark the midpoints.
Snap chalk lines from one midpoint to another to divide the space into four sections.
Add a dry row of tiles along the chalk lines, starting at the middle corner. Set tile spacers between each one to represent the tile joints that will be grouted.
Measure the length of space between the last full sized tile and the edge of the surface you're tiling. This space should be two inches or larger. If it's smaller than two inches, move the row of tiles past the center mark slightly to correct the issue.
Repeat steps three and four using the second chalk line. Once the tiles are spaced so that you never have to cut one smaller than two inches, the layout is complete, and you can start installing the tiles.