What is the typical 30-60-90 day plan for a PMM leader?

I love the power of a new perspective. I recommend an inspect, reflect, then suggest approach. Taking time to gather information from and form relationships with teams you support including product, sales, sales enablement/programs, marketing, as well as peers at your level will help you gauge your role's expectations and the business needs. Learning priorities, measures/OKRs/KPIs, recent learnings, challenges, and opportunities from these teams will help inform a perspective that will drive your approach and priorities as you ramp up. 

A typical 30-60-90 day plan for a PMM leader might include the following steps:

1. During the first 30 days on the job, the PMM leader should focus on getting to know the organization, its products, and its customers. This may involve meeting with key stakeholders, such as the product development team, the sales team, and the marketing team, to learn more about the organization's products, target market, and competitors. The PMM leader should also spend time learning about the organization's culture, processes, and systems, and should develop a thorough understanding of the product marketing function and its role within the organization.
2. During the next 30 days (days 31-60), the PMM leader should focus on developing a deep understanding of the target market and customer needs. This may involve conducting market research, such as surveys, interviews, or focus groups, to gather insights into customer pain points, preferences, and buying behaviors. The PMM leader should also develop a thorough understanding of the product's competitors and their positioning in the market.
3. During the final 30 days (days 61-90), the PMM leader should focus on developing and executing a GTM plan for the product. This may involve creating marketing collateral and messaging, identifying key customer segments and target markets, and working closely with the sales team to ensure that they are equipped to effectively promote and sell the product. The PMM leader should also develop metrics and KPIs to track the effectiveness of the GTM plan, and should regularly review and adjust the plan as needed to ensure its success.

My not helpful answer is that there is no "typical" 30-60-90 day plan. Your first 90 days will vary drastically depending on the stage of the company you are joining, the maturity of the product marketing team, and the specific challenges the company is facing. In my experience, the first 30 days are about learning and building relationships. The next 30 days are about aligning on a plan of action. And the next 90 days are executing that plan.