Place the ceiling tile on a flat surface with an old piece of wood underneath it to protect the surface.
Mark the desired measurements on the ceiling tile, using a tape measure. Use a pencil and a straight edge to draw lines on the tile where the cuts will be made.
Hold a hair dryer, running on high heat, 3 or 4 inches from the tile. Move the hair dryer over the entire surface of the tile for about 10 minutes. This will heat the tile all the way through and make it less brittle.
Score the pencil lines that you drew on the tile, using a utility knife. Run the utility knife over the lines several more times until it cuts all the way through the tile.