I came across a post today which concerned the method Richard Feynman used to tackle stuff he did not know. I use a version of that but it also includes stuff I think I know about because I'm pretty sure most of the stuff I think I know is fragile at best. Needless to say, notebooks play a prominent role. Ignorance is a handy marker here as well. Needless to say I have a lot of notebooks! So much stuff I don't know about or want to know more about.
Stuart Firestein has been mentioned else wiki his two books are useful:
Firestein, S. (2012). Ignorance : how it drives science (Kindle ed.). New York: Oxford University Press.
Firestein, S. (2016). Failure : why science is so successful. Oxford ; New York: Oxford University Press.
and Gleick's biography of Feynman is useful also:
Gleick, J. (1993). Genius : the life and science of Richard Feynman (1st ed.). New York: Vintage Books.