Reflections on a strange transition
The transition from IC to manager is a really tricky one, and something I don't see written about enough. There's a ton of advice for managers of all sorts (more on that later), but the specific phase of your first few days / weeks / months as a manager are something that could be more directly addressed. So, with the caveat that this answer may be somewhat unique to my own particular transition and personality, more than a general purpose guide to management -- here are some things I wish Future Joel had been able to tell New Manager Joel.
The hardest part of transitioning to becoming a manager was the wholesale swap of daily activities and impact on the organization. I got a huge high from doing IC work: Nailing a tough interaction, writing tight code, shipping product, and seeing the effects of the new feature across the product. Being a manager is more indirect: You help shape other peoples' ideas so that they can make good product decisions; You give advice to help improve an interaction; You put two people in touch around the organization to help them improve their work. All of this is really high impact, but day-to-day doesn't always feel that way. There were many days when I'd come home and think "Wait, what did I even do today? Would anyone even miss me if I didn't come to work next week?" Part of this is inevitable, so mostly I'd recommend you just ride it out patiently. A big part of that is my next piece of advice:
Despite it not feeling impactful on an hour-to-hour basis, your influence as a manager is real and significant. To really appreciate this I had to learn to see the effect I was having on my team and coworkers -- sharing a perspective on a problem and seeing it take shape in a new product; Even better, sharing a specific idea and seeing someone jump from that to an even better idea; Watching a designer kill it in a design review after many conversations about how to best present your work; Coworkers appreciating the work of your reports, and wanting to work with them again. It's important to notice and appreciate these, as reflections of your work. The next thing you'll notice is that these moments often very delayed from the work invested to achieve them. The feedback loop on this work can be slow, so it's important to be patient.
Any new role can feel terrifying at first. "Can I really do this? What if I screw up?" This was true of starting at Quora, and when I became a manager. The difference is that when I started at Quora as an IC, I could shield my coworkers from that terror, and just hustle to overcome it. I worked super hard by myself on the skills I wanted to build: did extra iterations of each design, triple-checked my code, read a lot on the internet from other designers, etc. As a manager, however, your job is definitionally interpersonal: you're having a lot of conversations, helping to make decisions, and giving advice to reports. There's no place to hide -- people will see how you're feeling and react to it. Even more than that, lack of confidence makes you worse at your job. The advice you give is weaker, and you reverse decisions and cause thrash on your team. So the best advice to overcome this is just "Fake it till you make it." Project calm and confidence even when you're terrified, and eventually it will be more authentic.
There is a large sea of very mediocre management books, that deservedly get a bad rep. But there are also some really fantastic ones that can provide useful frameworks for thinking about your new role. Pick an area that you want to improve on and seek out books in that area. Be discriminating in choosing the particular book, and be quick to stop reading ones that suck. But the gems can be really transformative. In the beginning, bias towards actionable advice over highfalutin' theories, then move up the abstraction ladder once you have more experience.
One unique property of management is that it's hard to model off your good coworkers because much of it happens in private. How do they conduct 1:1's? What kind of performance reviews do they write? How available are they to their reports? Rather than try and guess or infer this, just ask! Take seasoned managers out to lunch and just grill them on every specific question you have. Trust me, they had all the same questions too. Related to this: If you have a good manager, ask them questions, especially the non-obvious or hidden parts of management: "Do you run other 1:1's differently from ours? What went into writing my performance review? What work do you do for me that I don't see?"