Victor Lustig, the arch conman who sold the Eiffel tower for scrap, not once but twice, had a list of ten commandments for would-be conmen- they are rather interesting, very similar in fact to the kind of thing salesmen are taught today to employ with customers...
1. Be a patient listener (it is this, not fast talking, that gets a con man his coups).
3. Wait for the other person to reveal any political opinions, then agree with them.
4. Let the other person reveal religious views, then have the same ones.
5. Hint at sex talk, but don't follow it up unless the other person shows a strong interest.
6. Never discuss illness, unless some special concern is shown.
7. Never pry into a person's personal circumstances (they'll tell you all eventually).
8. Never boast - just let your importance be quietly obvious.
9. Never be untidy.
10. Never get drunk.