The Effective Executive: they concentrate on one task, if at all possible. After picking what needs to be done, set priorities and stick to them.
In Effective Executive, Peter Drucker shares some very great insight for becoming an effective executive such as organizing and managing your time, choosing your contribution to the organization, amplifying your strengths, setting the right priorities, and making effective decisions.
I highly recommend this Peter Drucker classic as it contains lots of anecdotes, insights, and practical examples on doing the right things effectively and making the right decisions daily.
Here are my favourite takeaways from reading, Effective Executive by Peter Drucker: