It is always a good idea to ensure that your limestone floors are dust and sand free. Debris left on the surface of limestone has a grinding, abrasive effect. A build-up of these will scratch the surface and make the stone vulnerable to further damage.
A simple way to minimise the effect of debris producing a grinding effect is to introduce barrier matting at entrances so that abrasive debris from shoes will not be transferred onto the stone, and to regularly vacuum or sweep. When vacuuming always ensure the brush attachment is connected, being careful not to scratch your limestone.
Your should periodically clean your limestone floors with lukewarm water. Use a well-wrung microfibre mop and use a minimal amount of water. Excess water can penetrate into your limestone, so be sure to dry your limestone when finished. Apply only light pressure while mopping. If you require a more thorough clean, use a pH neutral cleaner or an alkaline product specifically designed for stone.