The person who is controlling a conversation is the person who ask questions.
The best method you can use is asking open questions. When you ask your client instantly you will get more information, you will see the things he wants so you will know how you can help him. There is one very important thing you need to remember about while talking to your customer: create a friendly environment. The person you talk to has to feel relaxed and percieve you as a person interested in things you hear from him.
When he notice that you really care about him, he will become more open. More open with his needs and feelins but also more open to your advices and recommendations.
To revive a conversation start questions with: what, where, when, who, why, which.
These are the questions to which is not possible to answer simply yes or no. When your possible customer starts to talk you will reveal his deep needs. Later, by using such knowledge you can present your product or service in the way which shows the results he will get buying things you offer. Present how your product solves this special problem that your customer has. Awake his emotions: ask him how will he feel when this problem disappear, what would his life be like without experiencing this embarrassing situation ever again?
We all have things for which we would pay if somebody gives us a solution. If the problem is big enough, the customer is willing to pay more, just to eliminate inconveniences.
People don’t like when somebody tries to sell them something. That is why you should look that you care about him, but it has to be real. If you pretend it, this will have even worst effect. Other people will recognize it easily.