5 month old chow chow

Question
I got a 5 month old chow chow 3 days ago.  I got him from a backyard breeder.   know I shouldn't have but when I saw him I just felt so sad for him because I could tell he wasn't being well cared for so I took him anyway.  I have a chow/boxer and a Westie at home.  My chow/boxer is well behaved, obedient and friendly with other dogs and most people.  I have never had him so much as snap at anyone who visited our home.  I also have an 8 year old son.

Well shadow our new chow chow is extremely shy. I think he was mistreated previously because he literally shrank away from me when I was taking him out of the car to the house. He still won't come when I walk up to him though he wags his tail at the sight of me and my son but when we walk towards him he runs away.  I keep his leash on him in the house so that when I need to reach him I just step on the leash.  I know that I need to walk him regularly and take him out around lots of people to help socialize him but I'm wondering what else I can do to ensure that he is not aggressive with others, doesn't end up biting out of fear and apprehension and learns to come when I call him.  He has pretty much learned sit (in just 2 days - with treats and hand feeding) but I also want him to learn to come immediately when I call (as my Chow/Boxer and Westie do). I know that Chow Chows can be very difficult dogs especialy if they are not socialized appropriately so I want to make sure I do the right thing by Shadow as he is still pretty young.

Answer
It is good that he is young,that does make a huge difference-probably one way of telling if he is good with other people is to invite a friend over,and just watch the dog for a bit,before having him/her pet or try to pet Shadow

One way to get him used to others and to trust others is to have that friend offer him small treats even just for sniffing that person,and have him get really used to that person to the point where he will allow petting ect Then slowly introduce him to someone else,you can do this with a few people,but just one person at a time

Also taking him to obedience classes will also help him