One of the most underrated ways for a professional engineer to add value is to teach others. We learn to be students, individual contributors, project leads, and sometimes even people managers, often with plenty of formal guidance; but ironically, we're never really shown how to teach each other what we've learned. Here's some simple advice for teaching.
When explaining something, no matter how simple, err on the side of being too rudimentary. Don't assume anyone is already familiar with the basics. Start with whatever seems far too simple, and make sure you're building on common ground. I'm consistently amazed at how few software engineers understand how computers actually work; and on the flipside, I gather from the occasionally shocked facial expressions of coworkers that my knowledge of Computer Science has gaps big enough to drive a truck through.
When you state a fact or express an idea, pause to give your audience a chance to grok what you're saying. If they're not asking questions, you should be. Verify at each step that your students are still with you. If they might be paying you lip service (for whatever reason), ask pop questions that should be fast and easy for them to answer. The worst thing you can do is to presume you are being understood, and to proceed blithely apace without verifying that assumption.
Recognize opportunities to teach. For example, don't code merely to implement behavior. Code as though explaining to the reader what you wanted the computer to do (and add comments explaining why). API design presents a particularly teachable opportunity: Your API is not only a way for others to access your code, but a chance for you to show them how that code ought to be accessed, and what mental model they should have when considering problems in your domain. Great API design lets you frame the conversation.
A final word of advice is empathy. Whenever communicating information to other people, try to see things from their perspective. Don't stand on the principle of what you think they should know by now. Meet them where they are, not where they ought to be. Go out of your way to demonstrate patience, compassion and understanding. If you've had the privilege of being the student of a wonderful teacher or mentor, remember what you loved about them, and pay it forward.
Great piece! In the process of helping onboard two very new engineers to a new project so these are exactly the words I needed to hear.