How? You mean the specific items that would cause villagers to follow you around? Well it wouldn't matter too much to me, but I was thinking bread for the farmer, steak for the butcher, raw fish for the fisherman, a book for the librarian. Or it could just be bread for all types of villagers if adding that many new things would be troublesome. The follow mechanism is already in place for animals and the version for villagers would work exactly the same way.
I think this would make working with and managing villagers and villages much less frustrating. I also like the idea of different items for different villager types... adds a bit of RPG flavor to Minecraft by making the player match a proper motivation to each villager type. Support.