I’ll caveat this answer largely depends on your company’s goals, existing team structure, and culture. One should never parachute into a new company with a rigid 30/60/90 plan or assume the recipe for success in your last role will apply here.
First month = Big picture
Learn both your people and your products. Overload on 1:1s, get your hands dirty with the product, and speak to customers. “First seek to understand, then to be understood.”
First quarter = Build the basics
Hiring plan, messaging and positioning frameworks, etc. This could also be establishing the norms like announcement tiers and turnaround times or requirements like customer references before launch.
First year = Boom!
Once you have the understanding and foundation, this is when you can really start to have a more meaningful impact within the company. While you may play catch-up your first quarter launching products ready long before you arrived, the subsequent months are when you can demonstrate the value of a PMM to influence product and sales strategies if involved earlier. Definitely seek smaller wins earlier before this to establish some trust and credibility, but plan to get the basics established before steering the ship.