UIWeb (Scott Berkun) defines discoverability as “the ability for a user of a design to locate something that they need, in order to complete a certain task.” Some suggestions on what to focus on the UI:
Things that most people do, most often, should be prioritized first. Things that some people do, somewhat often, should come second. Things that few people do, infrequently, should come last.
If you want more detail, here is a deeper prioritization of how to think about the relative importance of tasks and features:
1. Things most people do, most often.
2. Things most people do, somewhat often.
3. Things some people do, most often.
4. Things some people do, somewhat often.
5. Things few people do, most often.
6. Things few people do, somewhat often.