True. I would also say that you spend a fair amount of time writing everything. I prepared a project management document that presented the scope and how we would handle changes. I would have meeting agendas, and then meeting notes. I worked very hard to not be surprised.
I have managed several projects (about 11, but do I count the ones that failed two minutes after kickoff?). Customer attitudes and the time line are also important .
One of my customers was easy to work with, because he was interested in having something than having something with all the bells and whistles. You manage customer expectations.
General rule - always tell the customer bad news as soon as you know it. They have to trust that you are in this with them. And telling them that something they wanted will not work the way they want or it will take longer to create, etc, demonstrates that you have an interest in keeping them involved and that it is not a us against them atmosphere.
It is much easier to manage a six month project than a six week project. A compressed timeline does not allow much time for error.
The challenge is learning enough of the customer's business fast enough so that you can translate it to the developers.
Prototyping is also important. After the reams of the kickoff documentation sometime later you bring them into a darkened room and show them a mock up of what they want. This is a chance for the developers and the client to talk. "Oh, you want it to do this."
Establish milestones, when possible. Keep everyone involved.
Quand on parle du loup, on en voit la queue