An interesting way that I introduced everyone was to have a good aligned character be accosted by a plot-hook giving NPC outside of town, telling him that the town was under attack by zombies. He then proceeded into the town, and went recruiting. He found the other players throughout the town, and they joined fr different reasons: One was hired by the town, one had lived there all his life and wanted to defend it, one was part of the town militia and was assigned to the task. Don't know if that would work for you, but it was a change of pace for my players.