Business models are the first leverage point. Separate the definition of the problem from the definition of the solution. The architect is the second leverage point.
Scenarios are the third leverage point.
Software developers must acknowledge that by definition, only the business people know the business. However, software developers can hypothesize what the requirements are likely to be. At some level of abstraction, everything is the same. The principles of unification , and process decomposition should be just standard tools in every software developer's repertoire. Use them wisely, and use them often.