2 words. Polar Diagrams. Write down the constraints you might want to optimise for. Size, cost of development/maintenance, complexity, you know your business (it's best that they be business related rather than purely technical). Decide on the relative importance of each. Keep dragging people back to the polar diagram. "But didn't we say that we needed to keep maintainability high?" or "didn't we say we wanted to ship right on time".