How would you recommend scaling a product marketing strategy for a series A start up? What would you prioritize after positioning/messaging and product market fit have been determined?

For series A or any early-stage start-up, I'd hyper-focus on really nailing product market fit (PMF) through deep engagement with customers who are actively using your products as part of their everyday workflow. In my experience, early stage start-ups have some early tech, a handful of early adopter customers (make sure you freshen up on Crossing the Chasm to not fall into early adopter traps) and a bunch of hypothesis that need proving (see the pitch deck for the A round). The first PMM at the company should work hand-in-hand with sales and product to obsessively, objectively validate what's real, what's defensible and what's repeatable. Don't take sales or product's word for it, see it in action for yourself. And don't go in with a bias to confirm internal hypotheses - assume the team is (at least partially) wrong, because statistically you are. And that's ok - keep working with customers until you see real patterns in what customers do post-sales with your product and what leads to renewals and expansion. Then write it down to see if you can to web copy or a pitch deck that can replicate the "so what" for a specific persona trying for a specific use case. Think one foot in front of the other rather than scaling out early signals - chances are you'll hit roadblocks that will force you to trace your steps back to a new set of customers using your product that'll require you to rework your web copy and pitch deck. PMMs at later-stage start-ups or enterprises need to focus on scaling out and simplifying a complex mix of products, audiences and use cases. If you're a (or the) PMM at an early stage start-up your job is much more hands-on and hand-crafted.