One night when my youngest was doing his homework, I went upstairs to see if I could help. Normally this involves me going back downstairs again very quickly.

'I'm looking for the lowest common denominator,' he said as I entered the room.

'Haven't they found that yet?' I quipped. "They were looking for it when I was your age."

Laugh? I thought we'd never start.

Then he said, 'Actually, Dad, there is something you can help me with. In Geography tomorrow I have to explain the relationship between the earth, the moon and the sun. I've got ten minutes to talk to the class about how it all works and how big they are in relation to each other and how far apart they are.'

He had all the information, ...

Get How to Persuade and Influence People: Powerful techniques to get your own way more often now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.