Threaten them, of course. No....kidding
I present the options and let my patients decide. It's their life, their goals, not mine. Many times, people will make choices that are ill advised, but they have the right to refuse and live at risk.
HOWEVER, safety for myself as well as other patients must also be a factor, so I will not allow someone's decision making to compromise the rest of us. There have been instances where I have had no choice but to use restraints or call for police protection, but this is rare, and after all other interventions have been unsucessful.
I find that building a trusting relationship really helps everyone involved. If patients truly value your opinion, they will be more inclined to follow their plan of care. Still, I remember this: it's their life, their value, not mine.