commuting to work

Hi All,
I have decided I am going to start commuting to my job as many days as I can. I have a NWT and the tires that originally came with it. I am trying to find out what is the best tire that would be good for commuting. I know with the tires that are on my bike, if I get near any sand or dirt, my bike slides easily. So if anyone can suggest a good set to get, I would appreciate it. Thanks and take care, Margaret in NY