To be an Effective Product Owner – (and this includes product managers and business analysts) you need at least four things. You may need more than these four, but these are common across all teams and domains.
Being a Product owner is more than then simply writing user stories and prioritizing a delay.
Yes, you need to know how to work with a development team and how to work on an agile style process. Yes, you need to be able to write user stories and acceptance criteria and you need to manage a delay and prioritize and participate in planning meetings.
But how do you know what should be a priority?
How do you know what will pay off, please customers? Satisfy stakeholders?
Product owners need to be able to do the work behind the backlog.
Product owners need to meet people, talk, analyze, and think behind these things. Anyone can choose random items form a backlog, but it takes skills and experience to maximize value.
Product owners need to be able to identify users, segment customers, interview people, understand their needs and jobs to be done. They need to know when to run experiments and when to turn to research magazines and market research. And this may mean that they also need data analysis skills.
If the product will sell as a commercial product, you will need broader product management skills.
You may also need specialized domain knowledge, some understanding of business strategy, finance, marketing, process analysis and design, user experience design and more.
Do not underestimate the skills and experience you need to be an effective product owner.
General rule: the more authority the Product Owner has, the more effective his role will be. The organization may confer this authority, but the team must recognize it and accept it as well.
Legitimacy is different from authority. Legitimacy is about being the right person, the person in good faith to exercise authority and do the background work to find out what they need.
Legitimacy means that the Product Owner can go and serve customers if they wish. And that means they will get their expenses paid.
Finally, and probably the most difficult … Product owners need time to do their job. They need time to meet clients and reflect on those meetings.