I think about essential thing to transmit the information that a person wants to know.
1) I should know what a person want to know.
2) I should know why a person wants to know.
3) I should know what a person knows.
4) I should explain the information that a person wants to know with the known thing of a person.
The first thing is so important. It is not surprising that the first thing. To tell the truth, the second thing is too important. I think that important thing is not only the first thing but also the second thing.