Situation is I have a number of in-house clients who continue to have trouble grasping the concept of defining clear requirements for a project and committing to them. Unfortunately my job situation is that I can't decline such projects, and I am often forced into situations that I can tell are doomed to scope creep (or worse) from the very start. Telling them that detailed requirements are vital and why we need them (using examples of past troubled projects due to this) have not helped.
I am looking for techniques, tips, words, etc that you might use to motivate or illuminate clients in such situations to the necessity of requirements,setting milestones, etc.
I am only a developer, and not a manager.