I have been working in Product Management for 9 years.
These are the 3 simple (but effective) pieces of advice I'd give anyone starting out (or who wants to get started):
Be Adaptable
You have to wear many hats when working in product management. Some days you have to be design-minded. Other days, you have to be more analytical.
The job requires flexibility and adapting to fill the role that the team needs at that moment in time.
Become comfortable in ambiguity and context switching because you'll be doing it often.
Ruthlessly Prioritize
When you first get started in Product Management, you're ready to conquer the world and build all the things.
You quickly realize, though, that building all of the things can lead you to build none of the things.
Saying yes to every single request that slides across your inbox or slack channel can lead to a scattered Frankenstein of features that don't make any sense together.
There's power in saying no and staying focused on the handful of things that will drive value.
Communication Styles Matter
Being a Product Manager means that you'll likely be interfacing with various stakeholders from within the company and externally.
The ability to tailor your communication to this wide range of personalities is imperative to ascertain and convey the information required to ship the best product.
When speaking with engineers, you might need to be more direct and analytical. Then later that day, you'll transition to speaking to the executive team, where you might have to speak in broader terms with a more high-level approach.
Determining the effective communication style for the situation will allow you to convey your message with clarity and ask the right questions to get to the root of the issue.
Honestly, I wish someone had told me these 3 things earlier in my career.
But I'm at least glad I can pass them along to you.