Rapport Building is indeed one of the most critical aspects of selling.
Many sales trainers suggest that you talk about something that your client is interested in especially if you have an interest in that as well, something like golf.
While this may build some rapport it is very difficult to move from discussing golf to discussing business without breaking that rapport that you have built.
If you build rapport at the unconscious level you can maintain it across a number of contexts.
You build rapport rapport by accentuating the similarities between you and your prospect and minimizing the differences.
So, if you go to see a prospect and they are feeling down don't bounce off the walls with enthusiasm, tone it down a bit.
Dress appropriately. If a prospect and his whole organization dress casually don't come in wearing a $1000 suit.
There are many ways to build rapport at the unconscious level and many of them are covered in my eBook on sales rapport
Hope this helps, Greg
PS: I sent you a copy of The Agreement Frame which you mentioned in your response to my "Helpful" Form.