For me a great starting point is the acronym DEEP:
D-etailed enough (is the Definition of Ready for the Features for the next 2-3 Sprints clear) 🧐
E-mergent (are you, your team and your stakeholders aware the the Product Backlog can and will change over time? Here is a lot of the business agility and flexibility everyone is looking for) 🤸
E-stimated (are the user stories estimated, supporting the POs with the next word – prioritised, and it helps the team to be aware of what is coming and what is the complexity of the user stories) 🃏
P-rioritised (is your Product Backlog prioritised and what are the measurements you are using: business value, risk reduction, dependancies) 🔝