You can make a suggestion, a request or a demand. What's the best approach? It depends. 

• Suggestions - encourage people to think about the situation and come to their own conclusions 
• Requests - allows people to come to their own conclusion with your guidance 
• Demands - require a lot of trust 

Whatever approach you take, the "because hack" will help. Follow your suggestion, request or demand with the word "because" and then provide 1 reason. 

People act in their self-interest. They'll act once you help them develop a sense of urgency.

Your relationship with the person will be put to the test. The more they trust you, the more likely they are to act on your suggestion or request.