I've been a manager for 14 months. I got promoted out of a senior IC role at a 300-person startup. Nobody told me anything useful beforehand. This is the list I wish existed.
I over-managed the work and under-managed the people. I knew how to review code, write good tickets, prioritize. I had no idea how to have a hard conversation with someone who was underperforming. The technical stuff was fine on day one. The people stuff took about 8 months to not feel terrible.
I thought my job was still to be the best engineer. It's not. It's to make my team effective. Those are very different things. When I jumped in to 'help' on technical problems I was usually just slowing things down and signaling that I didn't trust people.
I avoided the performance conversation too long. I had someone on my team who was struggling. I kept thinking they'd figure it out. Then I kept thinking I'd say something 'when the time was right.' By the time I said something, three months had passed and they were even more embedded in bad habits and I had less credibility because I'd been silent so long. Say the thing early. Kindly and directly, but early.
I didn't understand that 1:1s are for them, not me. I used to run mine like a status meeting. My IC peers told me this was a mistake. Now the agenda is mostly theirs. I ask about what's stuck, what they're worried about, what I can remove. It changed the dynamic.
I underestimated how much my mood affects the room. If I came into a team meeting visibly stressed or distracted, people noticed and calibrated. You don't get to be 'just having a bad day' the same way anymore.
Still figuring out: how to give really specific critical feedback without it feeling like a personal attack. If any experienced managers have frameworks for that, I'm all ears.