Ask HN: Best practices when working with teams

I work with web development for almost 10 years and I have always worked by myself. Now I have to manage a team of developers and I have no idea how to do it. In my head I already have everything solved, how the code should be done and so on... I don't know if I should tell everyone how things should be done (according with what I already have solved in my mind) or if I should let the team decide those things.

Another question is that I have always worked from the top down, I mean, I always implement the UI and work my way down from there. Now I need to separate concerns and I'm not so sure how that could be done efficiently.

I know that there are really smart guys here and I would greatly benefit from your advice. Thanks!