Do you have any advice for a technical person newly turned manager? Anything you wish someone had told you when you started as a manager / leader?
I can't think of a lot of generic advise: Sure, people I've talked to over the last 13 months of doing this face more or less the same problems, but how to best deal with them depends entirely on their situation, the people they work with and their own personality and skills.
One of the most eye opening things I've learned about is Cynefin from Dave (!) Snowden - wish someone had told me about it when I just started.
On the more generic side, I think the most important thing I wish someone told me is to not be _too_ humble, to trust my intuition and experience and be proud of my brand of management, not apologetic for not doing things the way somebody else read they're supposed to be done. Depending on your personality, I might as well recommend to be _more_ humble though - the balance is key for me.
This is totally what I think about managers of technical staff (and not "in some respects"). It's the subordinates that are doing the production; managers are lubricant, whose task is to ensure the production staff are maximally effective. Without effective management, production staff operate at reduced efficiency. But without production staff, managers are completely useless, and might as well be re-tasked to work as coffee boys.
I'm referring to line-managers, not the executives who make business decisions. I know nothing of executive work, and I suspect there's not a lot of continuity between line management and executive work. And yet some line-managers carry on as if they're already three-star generals.