If the countertop has a shiny surface any general purpose cleaner will do, spray, rinse off with wet sponge or cloth then dry. I make my own multisurface cleaner by mixing the general purpose cleaner of choice in water in a spray bottle. I like spic n span liquid or plain Mister Clean (not antibacterial).
Another great cleaner is as described by previous poster with vinegar. I omit the alcohol and add a little clear Ivory dish detergent. Indeed it can be used on windows as well.
You can use this on any type of countertop or other hard surfaces. If the unit is new you should have a manual that talks about countertop surfaces. If it is indeed sealed granite it may require resealing later on. That manual or a chat with the manufacturer will give you more tips on care.