Congratulation first.

Managing people is easy—but being a manager is not about managing people.

You have to be aware that managing is not as satisfying as coding and your goals have totally changed from now on.

- Learn to listen—that's so crucial—they're tons of techniques to get a better listener. Listening can be boring but these techniques enable you to listen hours (even with a smile on your face) without getting bored. It's so damn important that I stress it again: you should listen 95% and talk just 5% (from now on meetings aren't fun or a relaxing break, they become hard, boring work).

- Always 1-to-1 meetings—always. Every meeting with more than two people is worthless, try to avoid them, if you can't just keep them short and full of small-talk, fun and non-sense but without decisions. Harsh words, but leading is not anymore about cookie-cutting talks with colleagues. That's one of the big downsides of leading.

- Don't focus too much on your staff—look that they are happy and motivated (most important) and they have always challenging work, that's it. Don't try to be all the time around them—if they need help be there. Don't change your communication, just be yourself, but don't think they are your friends. Focus now on next steps within the company—you are now doing first steps in management and your work changed from working yourself to networking, to give and take and last but not least to power politics (if your startup is >100 employees). Look that you spend more time with peers from other departments and higher level peers in your company. If you can't progress or your company sucks in less than 12 months, look that you spend a lot time outside your company (there're lots of ways) and move on.

- Don't use tactics or manipulative techniques even if you are good in it. People always feels there's something wrong. Be yourself but keep distance.

- Get a mentor or coach with leadership experience in highly volatile environments, preferably outside the company

- Because working oneself is still most fun, look that you keep coding on private projects, even while in office (there're lots of ways). That's good for your own motivation and keeps your coding skills fresh. Otherwise you burnout after 6 months of all the meetings, mails and bullshit. That's important because from now on you will slowly loose close relationships within the corporation, upcoming relations are different, more political and it's important to stay grounded, meet lot of people (again leave your company often, go to meetups, because there you can just be yourself and that makes you happy; if you don't do this you'll quickly degenerate and get isolated because the working contacts are less and less true relationships). To officially code yourself is not an option anymore (which is sad) because after the first bigger mistake your management will tell your that you are not able to lead your folks when they see you coding with them (which would be better but non-technical management and c-level just don't get it)

These are all only very small hints without giving you the big picture which would take more time and there is no book giving a really deep understanding (I've seen many books before I had my first leadership position, none of them is written by real leaders).

If you want more advice: renmarksky at live.com