The value of Peter F. Drucker's teachings has been proven. Every manager or founder must read a portion of classical literature, among which must necessarily be a few books by the famous management theorist, or at least some of his articles.
This 2004 article gives us the definition of what Drucker calls an effective executive. For him, there are no stereotypes. He has known extroverted leaders, and others nearly reclusive ones.
What makes them effective according to Drucker is the application of 8 practices.
It starts with knowing how to ask "what's need to be done", and "what is right for the company", allowing them to collect the information they need, and ends with the expertise to hold productive meetings, and to use "we" rather than "I".
The effective executives also develop action plans, take responsibility for decisions, take responsibility for communicating and are focused on opportunity rather than problems.
Drucker details these practices in his article. If all this seems obvious, it is because today these practices are part of a foundation of knowledge and wisdom that business schools and corporate life can teach us. However, these essential principles are far from being systematically applied and deserve to be formalized, reminded and integrated into the startup's good practices.
An effective executive does not need to be a leader in the sense that the term is now most commonly used. What made them all effective is that they followed the same eight practices.