Nearly everyone agrees that accidental or unnecessary coupling is a bad thing and putting forces in place to prevent it is a good thing. In the software industry, we call those forces "encapsulation."
For an architect to get well-structured designs that shield unrelated things from one another, he or she will need to build a culture that values encapsulation. This is a mostly organic process, but it starts with someone demonstrating that encapsulation is important.
The architectural activities themselves can be modified to promote encapsulation by asking new questions, changing the old questions, and focusing on proper division of responsibility. These actions simultaneously help define more sustainable architectures and accelerate the transition toward a culture that holds encapsulation as one of its highest values.
Finally, the architect should take an active role in helping to upgrade and maintain the skills of the software developers on their team(s). A deep understanding of design patterns and true test-driven development will ensure that individual components are built correctly, promote better division and arrangement of components, and help instill a deep valuation of encapsulation throughout your development staff.