Know What to Know
Know Yourself and Develop Who You are
Constantly seek personal feedback and apply it with as much accountability as you can find. Spend regular time considering who you really are. Consider how you do against the golden rule. This one is preeminent over these that follow and were before this. Failure to be comfortable with your own skin is a key weakness. Failure to be so comfortable that you stop learning is the other ditch on this road.
Develop who you are more than developing your techniques. Who you are is the best base for great leadership. Example: A leader cares, or a leader can appear to care with great effort when needed. It comes off as too manipulative if it is not real. We need to have integrity and not simply avoid lying.
Know Your Employees
Seek to understand them and look out for their welfare. Employ them in accordance with their capabilities and work to help them understand their strengths and weaknesses.
Know Your Boss and Company Culture
You should make every effort to understand the next two layers of leadership that are over you. You should knowingly and with understanding bring all your value wherever you work. If your full value is not welcome, then find another place to work.
Know your Product/Service
Be technically proficient. But this should always be subordinate to proper leadership.
Know your Clients and Other Outside Stakeholders
The success of a firm depends on the quality of its relationships with a broad group of influential stakeholders. Develop long-term relationships across multiple domains. Seek understanding outside your own organization up, down and outward.