What should a Chief of Staff do in the first 90 days?

The first 30 days are for learning, not acting. Meet every executive stakeholder to understand their priorities and blockers — not to introduce yourself, but to listen. Map the informal power structure. Identify one small, visible quick win that makes the principal's work easier. Days 31 to 60 are for building an operating rhythm: a weekly priorities document, a consistent 1:1 cadence with the principal, and surfacing one structural problem with a point of view on what drives it. Days 61 to 90 are for proposing one structural change and having an explicit calibration conversation with the principal.

What is the biggest mistake a new Chief of Staff makes?

There are two equally damaging mistakes. The first is moving too fast — trying to demonstrate value by fixing things before building the trust and context that makes the value legible. The second is being so careful not to disrupt that the CoS becomes invisible. Both lead to the same outcome: a principal who is not sure what the CoS is actually doing. The first 30 days should be almost uncomfortably slow for a high-performer.

How does a Chief of Staff build credibility quickly?

Credibility in the CoS role is built through demonstrated understanding — of what the principal needs, what each executive stakeholder is working on, and what the organization's informal power structure actually looks like. It is not built by demonstrating competence before building that understanding. The practitioner who listens carefully in the first 30 days and then acts on what they heard consistently outperforms the one who arrives with a strategy before they know the terrain.

When should a Chief of Staff have their first 1:1 with the principal?

As soon as possible — ideally in the first week. The most important questions to ask in that first conversation: Have you had a Chief of Staff before, and what worked or did not? What are the two or three things keeping you up at night that are not on the public priorities list? What does success look like for this role at 90 days? These questions surface the information that shapes everything that follows.

What is the 90-day debrief for a Chief of Staff?

The 90-day debrief is an explicit calibration conversation between the Chief of Staff and their principal at the end of the first quarter — not a performance review, but a mutual assessment. The CoS asks: What am I doing that is most useful? What am I missing? Where do you want me spending more time? Then the CoS shares their own read: what they have learned about the organization, the structural problems they have identified, and what they believe the highest-value work is for the next 90 days. Most CoS skip this conversation. The ones who do not tend to have longer, more productive engagements.

The First 90 Days as a Chief of Staff: What to Do, When, and What to Avoid | CoS Certified

Chief of Staff Entry Framework

The First 90 Days as a Chief of Staff:
What to Do, When to Do It, and What to Avoid

Sherita Grinter, PMPSeptember 13, 20268 min readEntry Framework

The first 90 days in a Chief of Staff role set everything that follows. Get them right and you build the trust, access, and context that makes the rest of the role work. Get them wrong and you spend months recovering ground you should have built in week two.

I have watched this play out across twenty years of CoS-level work and more practitioner conversations than I can count. The failure mode almost never looks like incompetence. It looks like good judgment applied in the wrong sequence.

The Two Failure Modes

The Two Mistakes That Derail Most New Chiefs of Staff

Before the 30/60/90 framework, it is worth naming the two failure modes it is designed to avoid — because both are tempting, and both look like the right move until they are not.

Moving too fast. The new CoS arrives with energy, capability, and a genuine desire to demonstrate value. Within the first two weeks, they are proposing a restructured operating cadence, surfacing three structural problems to the principal, and beginning to redesign the leadership meeting format. Every one of those moves is substantively correct. None of them have the trust behind them to land. The exec team routes around the new CoS. The principal starts wondering whether they hired someone who listens. The CoS spends the next two months recovering credibility they should never have lost.

Becoming invisible. The opposite error is equally damaging. The new CoS is so careful not to disrupt that they produce nothing visible in the first month. They attend meetings, take notes, and say they are still in listening mode. The principal cannot explain what the CoS is doing. The exec team stops looping them in. The role quietly shrinks before it has a chance to grow.

The first 30 days should feel almost uncomfortably slow for a high-performer — because the work is absorption, not action. That discomfort is a signal you are doing it right.

Days 1–30

What the Right Sequence Actually Looks Like

The first thirty days belong to understanding — not fixing, not impressing, not proving yourself. The thirty days after that belong to building the operating system that makes the role functional. The final thirty belong to starting to lead at the level the role actually requires.

Each phase has a specific set of priorities, questions to ask, and milestones that tell you whether you are on track. The sequence is not intuitive — especially for high-performers who are used to demonstrating value through output. The CoS role in its first ninety days rewards a different instinct entirely.

Days before proposing any structural change — The practitioner who waits 30 days to understand before acting consistently outperforms the one who arrives with a strategy. The first month is reconnaissance, not intervention.

There is also a specific set of questions — to your principal, to each executive stakeholder, and to yourself at specific points in the first month — that unlock the information everything else depends on. Most new Chiefs of Staff improvise these conversations. The ones who prepare them structurally are at a measurable advantage by day thirty.

CoS Certified covers the complete 30/60/90 entry framework in Lesson 1.8 — including the week-by-week sequence, the question bank for the first thirty days, and the one conversation in week twelve that most Chiefs of Staff skip and almost universally wish they had not.

CoS Certified addresses the first ninety days in full — not as a generic onboarding checklist, but as a structured entry sequence built from what actually works across different organization types and principal relationships. Join the waitlist to be notified when enrollment opens.

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Sherita Grinter, PMP

Founder · CoS Certified · When The World Sees LLC

20+ years of CoS-level work across financial services, healthcare, and publicly traded real estate technology. Six Anthropic AI certifications. PMP, Google PM, ClickUp AI Expert. Richmond, Virginia.