As a manager myself, I do not feel fully qualified to tell you how to become the best manager (which is why I've framed it as becoming a better manager). I have spent a significant amount of time working with others, both in a management capacity and as a team member and there are some patterns and traits that I have noticed all great managers have that I want to highlight here that will hopefully help you become a better manager.
Don't micro manage
I have worked with managers who micro manage and with managers who haven't and I have met very few professionals who like being micro managed themselves. As I understand it, it is often a control thing - people who feel like they have to control everything in order to feel satisfied that they will get the outcomes that they want. If that describes you, you may not be getting the most from your team members if you do decide to micro manage. I sincerely believe that many professionals today are ambitious, know what they have to do, and will take the initiative to ask questions if they have any.
Remove roadblocks
Good managers try to enable their team for success - that is, they make sure that they have the right equipment, access, skills and resources to do their jobs successfully and effectively. If a team member is having problems with their computer, the manager is there to push things along to IT support and to make sure that fixing the computer is a priority. If a team member is having issues talking to stakeholders, the manager is their to facilitate the relationship and to figure out ways to mitigate.
Support as much as possible
I am currently working with a manager who asks on a regular basis: "What do you need from me? What do you need support with?" It gives me confidence that I can get any support I need from my manager and it encourages open dialogue. I have worked with managers who do not make it safe to raise issues or concerns and it ends up being a bad situation for the whole team because these issues are raised at the last minute when it may be too late to address.
Make it safe for dialogue
Back to my earlier point, managers have to make it safe for people to tell them about mistakes and issues that occur. I might be weirdly naive here but I think that as a manager, I want to make sure that people feel safe about telling me about mistakes. I will do my best to give credit where successes occur and to take responsibility when failures happen. You also want to make it safe for people to take risks because if people don't take risks, you may not be able to do things differently (innovate).
Leverage strengths and identify weaknesses
When teams come together, you are going to have some members of your team who are good at certain things and not so great at other things. As a manager, if you want to get the most out of your team, you need to identify these strengths and weaknesses and to figure out ways to focus on strengths as much as possible while minimizing work that people are weak in. The other thing you have to balance is what people want to get out of the project - maybe they want to develop skills in specific areas they are not strong in and as a manager, you also have to provide them with the opportunity to build those skills and experiences.
Facilitate dialog, resolve problems
As your team comes together, your role as a manager is to facilitate dialog and to make sure people are working together effectively. Are they communicating with each other? Are team members leveraging each other's strengths? What issues do you anticipate happening on the team and how can you mitigate them? Do you have several team members who want to play the same role on a team? How can you make sure that every member has equal or equivalent opportunity?
Manage stress
Managers, I think, should be good at reading team members and understanding their mood, stress level, energy levels and general work-life balance. If they understand these things, they can get more out of their team. Managers will know when to push a little bit on work, when to ease up on work activities and to manage deadlines and when to take a break every now and then to keep energy levels high. Managers know that people working 60+ hour work weeks is not sustainable. They know that if team members are happy, are getting the appropriate time to take vacation, and to have a life outside of work, they are going to be more effective.
Make it fun
Good managers know when to take a break from work and to just go out with the team members to have some fun. Maybe it's treating them to a special meal. Maybe it's organizing team building events. It's not just a way of team building, it is also a good way for managers to get to know their team outside of work.
Again, I have a long way to go before I become a great manager but I try to stay humble, I try to learn from others and I try to apply what I have learned to different situations to learn from experience.