My biggest advice is be customer-focused.
I am a big believer in PMM being a strategic partner to Product Management.
Beyond this simply being my belief, it is hard to build a strong PMM organization unless the business sees the function as strategic. One of the ways in which I've helped Product Marketing to be viewed as an important and strategic function of the business is by influencing the product roadmap.
Each PMM on my team - including myself - is involved at Product Discovery. The reason we're involved is that we come into the discussion with a strong understanding of the market, our customer (in particular the buyer persona), the competitive landscape, win-loss data within sales, campaign performance, and with data on how our products are performing (e.g. pipeline/bookings) by region/customer/by channel.
At Snow, we subscribe to the notion that Product Marketing is measurable. The PM role is simply too large to own all of what I just described in the last paragraph. If you are known as someone who understands the customer and you are in possession of data than can help support product in prioritization, then you can get that set at the Product table that you are seeking.