I went to my 30th high school reunion over the weekend. One thing that was pretty fun about it was being in a room where almost everyone was nearly exactly my age and had spent their adolescence in the place where I did. That combination helped strip away some of the normal juggling one needs to do at parties when meeting people.
One phrase that worked well for me (because it was true): "I certainly remember your name, but I don't remember how well we knew each other."