Should one start their scrap-work / mockups in an ordinary notebook or scrap-paper to be thrown away ? 

What is the recommended practice? 

* Keep older drawings ?
* Throw them away ?

Is it better to sketch in pen or pencil ?

* Produce permanent work ?
* Leave space for change ?

Is there an attachment similar to Moleskine that can be made with Graphic design practice ? I have seen some carry around large drawing pads/books. Unfortunately I am on the move and would prefer something a bit smaller.

To sum up the question : 

*Is there a certain format AIGA (that is the association for Designers right ?) recommends people to use for preliminary design ?*