I would like to improve in writing goal-oriented user stories/features

Question

I would like to improve my user stories writing abilities so I need your experience and guidance. I think that each variable part of a user story can be improved by following certain guidelines.

1. Role

Defining possible roles may be the easiest part. The only problem is that user stories usually just describe functional features that need development.

• Do you write non-functional stories? And I'm not thinking about technical stories that are related to other aspects of product planning like administrative things. I'm more thinking of additional supporting stories that support the same high-level goal. Like advertising related stories that are related to features?

2. Feature

Defining features seems to be easy but it turns out it's not. Because I can see stories that are heavily related so certain roles can't be developed until others are finished. Example: User registration is a pillar user story that needs to be done first in order to develop other user stories that are related to registered user roles (logged in users and/or admins etc.). This one is very obvious but sometimes relationships are much more subtle.

• How do you avoid relationships between user stories? Is there a technique to break related stories apart so we can have better development parallelism? Breaking relationships also helps better sprint cycles because one story can't stall the whole sprint.

3. Benefit

This one is the hardest part that I think I have least knowledge how to write good user stories with clear benefits.

• Do you actually write benefits per story or do you rather provide high level goals instead? Providing these instead of benefits makes it easy to see why certain user story is more important than the other? So it helps prioritisation.
• Is it wise to have shared benefits/goals between set of user stories?
• Do you write user stories without benefits part? Is that wise and what do you do instead?
• Do you write benefits in a way so they can be measurable? Can we do that and is it beneficial?

4. User stories as a whole

• Have you ever defined all user stories as epics? This would help filter out/prioritise those that give more to the common goals. Then split them into digestible chunks or per single feature user-stories.
• What additional metadata do you add to user stories? Also talking about user story grouping per higher feature or goal...