I was looking through the nameberry name game forum because they tend to have a lot of interesting games and I found this one.
It's pretty simple. You leave four names, boys or girls (I suppose it doesn't matter if they're all the same gender or not), and the next person puts one into each Hogwarts house--Gryffindor, Slytherin, Hufflepuff, and Ravenclaw--and then lists four more names for the next person. Easy enough, right?
You can give reasons for sorting the names the way you did if you want to, but it's not necessary.
Amanda, Leah, Scarlett, Jane