I would also add: get to know your debugging tools really well. I'm constantly surprised how many developers still use print logging to debug issues with data s

I would also add: get to know your debugging tools really well. I'm constantly surprised how many developers still use print logging to debug issues with data structures. Sometimes it's hard to visualize what's going on in your mind or with the code, why not let the computer "play computer" and actually see what it's doing step by step. We may not have the real time integration that Bret Victor demos, but a call stack, watch list and breakpoints are a beautiful thing when you know how to use them. A REPL like Ruby's pry is also invaluable for exploring return data and playing with data access syntax right in the console without long tedious trial by error sessions. (I know this annoys the purists who think you should know the data structures beforehand -- they are right; if you know what you are doing, of course you'll be fast -- but sometimes even the smartest of us don't know a service api changed without popping the hood. Use all the tools you can to understand what your code is really doing, not just what you think it's doing.