I work on over 30 files at a time that can last years on end. I find that the best system for me is a Bring Forward System that lets me know exactly what needs to be done today. For every file I work on I create SMART tasks based on a file plan.

Using the Smart Lists in RTM I input "due:Today AND tag:@work" to create a Bring Forward List for work.

I also have a similar list for personal tasks. I tag each task on everyone of my lists with the list name, so I can easily identify the file that the task relates to.

At the beginning of the day, I use RTM's priorty system to determine what needs to be completed today, what should be completed today, and what would be nice to complete today. This provides a nice neat list of tasks that I should work on today.

When I have completed the task, I mark the task complete and look at the task list and the file to make sure that it is on track with the file plan. If everything is ok, then arrange when I will look at the file again and what the next action item should be according to the file plan.