UserStories are sometimes difficult to break down into 2-3 week iterations (I don't think 1 week iterations can work). Say the customer has given you story cards x, y and z, and doesn't mind the order in which the stories are implemented, since he needs all of them to make his customers happy. You decide to concentrate on story y because you expect this feature to indentify and expose most of your core abstractions. This is desirable, helping you to build a foundation which will enable you to easily add the remaining stories. Even though you will only add what is necessary upfront, this first story will prove to be much more expensive than implementing subsequent stories. This is something that you and your customer should be aware of when planning releases. --AdrianCumiskey
PlanningUserStories