I assume from the downvoting that this isn't a very popular approach.
EDIT: To respond to the issue of the arguable merits of my post — I made my post because the majority of comments here are describing preparatory activities performed on one's computer. I wanted to give some of my non-computer related warmups, since they can also apply to projects that aren't necessarily software-oriented.
But I always find myself going back tot he notebooks once or twice to refresh myself on one detail, look up a particular incantation, whatever. It's nice to have them in reserve for that.