In Scientology one of the ways to do this was to address the person's views on "help". Is it okay for others to help you? Have you ever helped anyone else? What if your car broke down by the road, would you refuse help to get it back running? If it was a friend or family member who offered to help?
It doesn't take long to make people see that we trust people to help us all the time, often with big, important things, often without thinking about it. Once someone is open to the idea of help in general, it's not a huge leap to show them that the organization is there to help them, and that it's okay to accept the help. Challenging someone's views on control is sometimes required as well, done in a similar manner.
A follow-up tactic is to find someone's "ruin". Everyone's got something they will trigger on. Health, depression, family, money, career, whatever. It's usually very easy to get people to volunteer this, sometimes you can just do a cold read of someone and know right away without even talking about it, it's the same thing a fortune teller does. So, you offer to help them with their ruin.
There's nothing magical about it, and it works on everyone if skillfully applied, even if they have their guard up in advance and have heard all kinds of awful things about you. You aren't forcing people to do anything, you're not being dishonest or tricking them. Everything is above-board. The hard sell comes later, when a deeper level trust has been established over time.