Loops Are Your Friend

The best practice is to iterate and deliver incrementally, treating each iteration as a closed-end “mini-project,” including complete requirements, design, coding integration, testing, and internal delivery. On the iteration deadline, deliver the (fully-tested, fully-integrated) system thus far to internal stakeholders. Solicit their feedback on that work, and fold that feedback into the plan for the next iteration.

(from “How Agile Projects Succeed”⁴)

While the waterfall with feedback model recognizes that all the requirements aren't typically known in advance, and that mistakes will be made in architectural design and detailed design, it doesn't go far enough in taking those realizations into the process. Iterative process models make this required change in process steps more explicit and create process models that build products a piece at a time.