I agree on the neutral territory meeting. I would have them meet up as much as possible before the actual move in date. that's what I did with my dog when I moved in with my DH and his two dogs. I even did a few sleep overs with them before the big move. Dogs will have to sort out their pack status too so, there may be some agressive moments. I usually just let them sort it out themselves unless one dog is being hurt badly.

I got lucky because my dog (Lab) adapted well with the two new dogs my DH had. She even took to the Airedale like they were long lost friends. It was funny because the smallest (Shih-Tzu) is the pack leader. My Lab wouln't even look at her when she was eating for the longest time and was very submissive. Now they have eased into a beautiful relationship.