Clarity of team responsibilities
Since you will be managing a team of developers, and perhaps some business analysts and architects as well if you become a Project Manager, your individual team members' roles will generally be well defined.
In any case, one of the main responsibilities and essential skills of a manager is to ensure that their team knows what is expected of them. So, establishing a crystal-clear clarity of your team's structure and each member's responsibilities is almost always a valuable exercise.
However, from my experience, I find that new managers have a propensity to shy away from doing this. This can be mostly attributed to the impostor syndrome, where the manager feels it's necessary to assume that everyone knows their role already. With the manager assuming that they themselves already know, or that they need to be seen to know, so then it would be a silly and embarrassing question to ask. But that is exactly what they should do!
Having an honest discussion about the identity and purpose of the team and its members can have multiple positive effects. It improves internal communication by opening up the floor, giving everyone a chance to speak up, and establishing a behavioral norm of discussing anything and everything where necessary. Remember that something obvious to one person may not be to another, and your role as a manager is to facilitate the sharing of knowledge among the team. You may well find that at least one member of your team wasn't fully aware of their roles, or others', and was too nervous to ask.
By openly discussing the team's collective and individual responsibilities, you can also identify and unlock ideas for improvement that were previously hidden.
The only scenario in which reclarifying each team member's responsibilities may not be necessary is when the team and overall organization's culture is so mature that an inherent understanding and fungibility exists without question. This is usually only found in a specialized smaller team, and often in a startup environment, which, by its nature, requires its staff to perform many roles. Therefore, defining an exhaustive list of these roles and responsibilities can be a limiting exercise and end up being counterproductive.
The most widely accepted and well-used method of clarifying responsibilities is the Responsibility Assignment Matrix, also known as the RACI model. RACI stands for Responsible, Accountable, Consulted, and Informed.
Source: http://www.ascendforairlines.com/2016-issue-no-2/right-people-right-places-right-results
If you're managing a large project with many cross-functional team members, it is important that everyone is clear about their roles and responsibilities. The preceding table gives you an example of a RACI table in action.