Suppose you work in the software industry, and your job is to research and debug new software. My problem is that research takes me in many unpredictable directions, and debugging is even more unpredictable -- so it is difficult to get very granular with next actions. On the other hand, if you just define an action item as 'debug feature x', you may have an action item that takes days, which is not as granular as I would like it.

What approach would you suggest that would give me sharp easily-visualizable next actions of the correct granularity?