I think I am pretty good at remembering names, but for me I have to see the names written out so I can picture the name in my head to go with the face. When I meet someone (kid or adult) with an unusual name, I will ask them how it is spelled. Until I can see it in writing in my head, I can't remember it.
With my own class, I saw most of the students' photos ahead of time on their placement cards, and I studied those. They were really surprised when I called them by name on the first day!
Other than that, I just repeat their name back to them, like others have said. "Hi, Bob, I'm happy you're in our class!" or something like that.