For those of you who aren't familiar with Jason Horejs, owner of Xandau Gallery in Scottsdale, AZ, he's a wonderful writer as well. His blog has some of the most insightful information (outside of AFI of course) you may run across. His latest post is all about what NOT to say when closing a sale. I think you might find it helpful. I know I did.
You can find it on the reddot blog, here.