Mind mapping is part of the activation process you use it along with Superreading and dipping, skittering to activate. With each activation pass you add more details to your mind map. The stating point of the mind map will depend on your purpose.
Don't just sit there waiting for your brain to start filling the blank page 
Get active start by asking questions, check the book and activate for answers. Record information that is important to you on a mind map.
Alex
