I use SCI granite cleaner sold at home depot. I also purchased my granite through them. My granite has a 15 or 20 year warranty on the seal. I would check with the company you purchased through to see what kind of seal you have and if there is a warranty. I have heard some people say granite needs to be sealed every year. With that said sealing is easy wipe on leave for a while buff off. SCI also sells a cleaner and preserver in one. I do not like it as well as the straight cleaner. It leaves a film and requires alot of buffing to get it off. It does however leave it super shiny and smooth so I only use that one occasionally.
@Samof5 Thanks so much for your help.
For cleaner a couple drops of dish soap and plain warm water.
Sealer may or may not be needed depending on the "stone type" Check out this report from an industry leader in stone care.
@KMS Woodworks Thank you for the thorough report!!