Dr. Sophia Yin created this great checklist for socialization.
Download it for free on her website.
I will be printing it out and filling it in as we raise Oso II. It's really well done and I highly recommend it!
She also has an e-book, I haven't bought it yet, I'm not sure if I will. I am inundated with reading material. I am truly enjoying the information on her blog and learning a lot though, so I may consider it.