lendini

hi all wandering if you lot can tell me what types of tiles need sealing ie polished porcelain ,slate etc and the ways in which you guys go about it.are they sealed to stop staining.also do you use stain stop vfor the sealing and what do you use to clean tiles if you get marks on them when you have layed them before sealing and grouting i.e coffee,finger marks and adhesive.
can all these be cut with dry cutter and wet cutter.thank you so much in advance Lee