Slow and steady, then go at his pace
Some dogs need a lot of time before they really adapt to the world and others jump in to make up for lost time. You pretty much get to wing it with each dog.
Building confidence is the cornerstone for socialization. Quick, simple exercises -- successful sits, anything -- each time before you go into a social situation, then, if things get too intense, remove him from the situation and go back and reinforce his confidence with a few of those simple successes again.