From just landing to now landing & expanding accounts

I'm an AE at a SaaS startup in the data transformation space, and I previously was solely tasked with net-new ARR. Once the account closed, I lobbed it over the fence to Customer Success and I was onto the next one -- deuces!

We've since decided to change course internally and I'm now responsible for both landing and expanding accounts. I don't have any prior experience doing post-sales work, so I'm really hoping to hear quality feedback on the best way my fellow sellers navigate the post-sales motion on top of landing accounts.

For example, do you create a system that prioritizes certain customers over others? How often do you meet with the account/do you always loop in your SA/SE? Do you proactively schedule monthly calls or position more ad-hoc support?

Any/all feedback is appreciated! I'm also glad to share more context if necessary.