How long does it take for you to feel comfortable making fast, high-impact decisions when you’re in a new leadership role? What’s your secret to getting comfortable quickly?

I think that in order to make a confident and accurate decision in a new position, it depends on your understanding of the organization and mission. It is likely that you fully understand the purpose of the organization, so you should start by understanding the issues that each member is thinking about through communication with team members, etc. It can be said that accurate decisions should be the best strategy in the mission and at the same time to increase their motivation and the organization to move actively. I think leadership is the one that motivates team members and produces the best results.

I agree that there is more to this topic than finding comfort in decision-making in a silo. The secret to effective leadership is being able to distinguish between decisions that require collaboration and those that don't (to Michael's point about types of decision making). Good collaborators know when not to collaborate (while making all people feel like their input matters). And, when in a cross-functional role or dealing with several teams, you have to learn quickly how to 'weight' each decision. A Regulatory SME shouldn't have the same weight on go-to-market strategy as someone in Strategic Marketing.

Leaders make three types of decisions - unilateral, informed, and collaborative.
- Unilateral, is where you don't seek input from others and inform people of your decision. You then inform them of what needs to occur, i.e., their role in its implementation. Some people never get comfortable with these, while others are overly comfortable. Generally, you'll use unilateral decisions sparingly. 
- Informed, is where you seek input from others, make your decision, and explain their role in implementing it. These are the most frequent in the management layer.
- Collaborative is where you say to others, 'We need to make a decision', and bring your assumptions, goals, concerns, and other thoughts into the dialogue. You don't make a decision; the group does. They are for the more strategic, high-impact decisions. 

Note that being good at collaborative decision-making enhances your informed and unilateral decision-making.

In terms of being comfortable making these decisions, bear in mind that there is a dynamic in decision-making of valid/invalid confidence. Too many people have invalid confidence in their decisions, creating logical and compelling decisions that are false positives and struggle in implementation. 

The question as posted is incomplete. It would be better to ask, 'How long does it take for you to feel validly comfortable making high-impact decisions where the decision has the fit, feasibility, and alignment for it to be likely to succeed, balanced against a short time window and limited time availability?' i.e., The optimal decision.

There is no simple answer in terms of weeks, months, or years. However, if you focus on the decision-making process you use and commit to doing it right, not lying to yourself, not taking risky shortcuts, etc., that's the fastest path to valid confidence. 

(SchellingPoint is an applied research firm specializing in leadership decision-making. It operates the largest database of real-time, leader-led group decisions.)