From Lists of Note, the 10 Commandments for Con Men as set out by Victor Lustig a con-legend who once took $5K off Al Capone and sold the Eiffel Tower.
1. Be a patient listener (it is this, not fast talking, that gets a con-man his coups).
2. Never look bored.
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 fellow 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.