How to do top task analysis?
List the Tasks. In the users' language, identify features, content and functionality you want them to consider. Avoid internal jargon as much as possible and have it at a level of granularity that is both actionable and that the user can relate to. The tasks can be specific to a website or to a class of websites.
What really matters focusing on top tasks?
Get them wrong, and chances are you'll lose the customer. Top Tasks Management is a model that says: “Focus on what really matters (the top tasks) and defocus on what matters less (the tiny tasks).” Tiny tasks are a nightmare for web teams. On their own, these tasks seem innocent enough.