Before you leave thank the person for their time, and make sure you have their name, address, and phone number. Say something you liked about talking to them. Repeat the commitment they made. After you leave make any notes you need to about the person or the visit. It doesn't happen that often.
People are often pleased to be asked for their thoughts and given opportunities to get involved.
However, it does happen. The key thing is not to take it personally. If someone says they don't want to talk to you, try to find out why. If it isn't a good time then ask when would be a good time to come back - and make a note of it. Here are a few more tips.