A tip to ensuring that your product selection is appropriate for your floor is to test it on an inconspicuous area. Never use bleach and always apply the cleaning agent with a soft cloth or mop. Try not to over wet the floor and ensure that all residue is rinsed away. Residue left on the tiles will attract dirt and the result will be dirtier tiles than you started with.
Specific brushes are available to deep clean grout lines. Be careful when cleaning the surface of your tiles as dirt can easily be pushed into the grout lines. Grout is porous, so this means it will get dirty very quickly. The dirt gets ingrained and can be a real challenge to remove. Grout brushes work to clean the grout without damaging it.
Stone floors, whether manmade or natural do experience general deterioration over time. This may mean that the surface seal has been degraded. Therefore, a stone sealer may need to be applied to ensure the tiles are equipped to repel daily wear and tear once again.
It is always wise to seek the assistance of a professional stone cleaning and restoration specialist. The reason for this is that they are equipped with the professional machinery and products to deep clean your tiles and grout prior to re-sealing the surface. They are also able to fully restore your stone floors, should they be in such a deteriorated state. The end goal of restoring your stone floors is to achieve the appearance of newly laid tiles (or as close to that as possible).
This process effectively removes all old surface coatings, repairs any damage to the tiles and grout and grinds the surface of the tiles to reveal the undamaged surface underneath. Natural stone and manmade tile require individual approaches as their care demands are very different. Part of this process is to deep clean the grout lines and seal them again so that the entire floor returns to its best-possible appearance. The transformations can be incredible.