Especially when I am coming into a project already in flight, I like to ask the team, the sponsors, and the stakeholders what they think we are out to accomplish. I get different answers from all of them, generally, but it tells me what and where the inevitable disconnects are. After that, the task is to get everyone back onto the same page.
There has been a cartoon around for years showing the design of a swing in a tree drawn several ways. You can find a copy here:
http://www.soloseo.com/blog/2007/11/03/what-the-customer-actually-wanted/ Better than anything else I have seen, this really clarifies how disconnect can impact a project and thus insure that you will fail to deliver what the customer (business) wants. Even when everyone is managing to the written plan, it is possible and even probable that understanding will shift. Regular checks with business, stakeholders, and team will insure that everyone continues to see the same goal the same way.
Edit: formatting
