Cash Register Expectations?

So this is my first job at WDW (Walt Disney World) I work in the Cash Registers. Of course since Disney is a Happy place I have to project positive and respectful Attitude. I find my self lacking in what to say to a person when they come up to me to order something . I wonder... what is your Expectations of the person working in the cash register? What do you expect us to say? Do? That way a person can have a good experience even if its the person at the cash register.