Certainly, there are interpersonal and relational aspects of a client/vendor relationship that are vital to long-term partnership success. After all, who wants to work with a jerk or an insenstive boor (on either side)? ;>}
But those skills are not enough to make projects go smoothly. One of the most important practices that any client can cultivate is a great process for spelling out project requirements.
Here is a very helpful article on the outsourcing process (including a good definition of the acronyms RFI/RFQ/RFP), reinforcing many of the skills and behaviors that I have seen work well over the years.
A pull quote:
The quality of proposals you receive will only be as good as the RFPs you send to them. If you do a poor job of articulating your needs, the supplier must speculate and make assumptions. Being vague communicates to the supplier that you are not sure of your own needs. Your objective is to get the supplier to put forth their best proposal.
Read the whole article. There is an art and science to drawing up good proposals, and projects often go off the rails not because the developer is “bad,” but because there simply weren’t enough details to get on the right track.