When to use it
Use it when you are stuck and unable to shift thinking to other modes.
Use it when you want to do something that has not been done before.
How to use it
Think about what you are thinking about, and then think about what you are not thinking about.
When you are looking at something (or otherwise sensing), notice what is not there.
Watch people and notice what they do not do.
Make lists of things to remember that you normally forget.
In other words, deliberately and carefully think about what is absent.
An artist draws the spaces between things.
A market manager for a furniture wonders about product areas where customers have made no comment. She watches them using tables and notes that they leave the tables out when not using them. She invents a table that can be easily be folded and stored.
How it works
The psychology of thought is such that we are very good at seeing what is there, but not at all good at seeing what is not there. Absence Thinking compensates for this by deliberately forcing us to do what we do not naturally do.