A book I recommend to anyone new to a management role: High Output Management by Andy Grove

Of several great takeaways in this book, a simple framework for prioritizing time spent as a manager is my favorite:

Four patternistic actions:

• Information Gathering
• Nudging
• Decision Making
• Being A Role Model

And the four anti-pattern actions while doing the above:

• Delaying decisions
• Meddling
• Abdication
• Unnecessary interruption. 

This is a great post that gets into more detail on the positive four, and includes an example day-in-the-life. The TLDR? Do more activities that map to the patternistic actions, avoid activities that map to the anti-patterns.