REPL driven development. I was doing it before Clojurists were talking about it. It's the most efficient way I know to build large systems -- by composing small

REPL driven development. I was doing it before Clojurists were talking about it. It's the most efficient way I know to build large systems -- by composing smaller pieces whose API and behavior you are deeply familiar with through interactive fiddling. Relatedly, learning to use Emacs with power and precision has been a boon to me, though the Emacs skill ceiling is absurdly, absurdly high and there's so much I've yet to learn. Programming the editor to do repetitive work for me, not just using packages and customizations, is key. Literate programming has been a tool in my toolkit for documenting my thoughts as I solve an interesting problem. These days I use org-mode, but noweb has been useful in the past.