The above post implies that you are going to use a waterfall type development methodology. A more light weight alternative is to do iterative development. Deliver a release to the customer every 4 - 6 weeks, and ask if that is what they want. After each one, if they like what they see, ask what they want to see in the next iteration. Negotiate the scope of each iteration, but not the customers priorities.

Of course, if they don't like what they see, you have a different problem. Figure out how to get on the right track.

I get email on my yahoo account all the time either for buying prescription drugs or sex sites, or some combination of the two (Viagra). I didn't subscribe to any of this. That is an accident as far as I'm concerned.