How to solve problems. Every developer should read Polya's "How to Solve It".
"How to solve it" by G. Polya or "How to solve it by Compute" by R. G. Dromey?
Adding to the list.
Debugging strategies: Eliminating variables and addressing your own assumptions about the system in order to debug effectively. I think this fundamentally applies to all subsections of our industry.
Write maintainable code from the start.
What do you mean by know? Are you referring to languages and technologies, or are you talking about... refactoring, planning and things that are not strictly related to development? Because I would love to talk about either, but one is definitely shorter to write. :)
Sometimes the best way to solve a technical problem is to go for a walk
I'm saying what some would assume is obvious, but I'll say it anyways. It's OK to ask questions. No one knows everything. What you should do though before asking your questions is do your due diligence. Step through the code, check the logs, Google the error etc.
Someone more junior would perhaps due less of this, but as you progress in your career your diligence should increase.
Part of being a software developer is being a detective. 🔎 Now crack the case! 😉
How to talk to people. This has become a dark art.
That when people say "oh [X person] is just difficult to deal with - they're a fantastic engineer but they have no people skills", they shouldn't think that this is okay, and they _definitely shouldn't aspire to be that person.
Everything and 42.
Design and UX specially
How a computer works.
How to google stuff :)
Every developer should understand how their tools work. That is, OS, IDE, text editors, shell/command prompt
They should know the seven commandments and keep them in the drawer for easy reference:
Snickers, Toblerone, Ritter Sport, Nestle Crunch, Almond Joy, Kit Kat, Milky Way
Every developer should know how to learn and do research
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