At Srijan, we transformed our methodologies from a classic waterfall approach to semi agile process, and now we are implementing a full-on agile Scrum inspired approach to work on Drupal projects. In the ongoing DrupalCon Barcelona, there was a session on Waterfall and Agile.
Agile for clients who still don't understand the concept.
Presenters of the Session.
Interestingly @adaptdk used the very same example that I had given in my talk at DrupalCamp Australia!
Don't build a Car at once, build a shippable product every sprint. Start with a unicycle and achieve the car
Manauwar from our team also shared a tid-bit on Agile.
Waterfall model means the client is going to pay for features that he might not even use - A valid point which I also used in my talk.
Sprint Planning is a good time to do and review the estimates.
Talk in terms of Story Points. Atleast for the Stories!