Sometimes, you let people take a large risk and trip, without being there to catch them. Even powerful people can take a hard fall.

In other circumstances, its easier to let them think they're working for something within their own self-interests, when it is in fact yours.

Or you can be honest. Sometimes powerful people simply aren't expecting frankness. But you need to find meeting ground where their powers don't hold so much weight. Or you must decide that you have little left to lose.