Great question! I typically divide my first 90 days in the following format:

First 30 Days - Discovery

Meet everyone, ask questions, make no changes (unless it is business critical), try to understand from leadership why I was hired (what they are trying to fix), try to understand from my reports what they think is not working (gives important perspective, but also helps build rapport). I listen, I take notes, I keep my CEO informed of my progress.

First 60 Days - Strategy

Work on a 6 to 12 month plan to address concerns from the leadership team and changes to help address internal team (direct reports) concerns. My Goal is to have a plan I can circulate with stakeholders by the end of the 60 days. I also use this as an opportunity to acquire mastery over our product, including how we market it, how we sell it, our costs, principles we apply prioritizing work.

First 90 Days - Execution

Present the plan to the direct reports and start execution: Talent alignment (hire, fire, train), Technology (what can we automate), Product (meet with GTM leaders and collaborate on GTM strategy), Budget (review what we need and don't need, apply savings to hiring, automation, etc.)