Consistent project success requires your organization have a systematic approach to eliciting, organizing and documenting the system requirements, and establishing and maintaining agreement between the customer and the project team on changing requirements.
As the saying goes, pictures tell the story. Having the right visual models will help your team connect the systems and simplify the IT landscape by helping you stitch the proper design patterns and illuminating common components and business logic.
Ensuring that all stakeholders have a clear understanding of the requirements is a leading factor for project success. Everything revolves around these, irregardless of the methodology you follow. Misinterpretation of requirements by different stakeholders is a recipe for churn, confusion, defects, project delays, and disappointed business sponsors.