As you'll have read on this thread, the key thing you need to decide about your project is whether it's:
- Active
- in which case, it should always have at least one next action or waiting for against it, to ensure that it's moving forward. You'll pick this up in the weekly review if you haven't during the course of the week.
- Inactive - which could be either:
- On Hold
- You've made a commitment to get the project done, but you just can't get to it right now, so it's on hold and then during a weekly review you'll decide whether to re-activate the project or re-negotiate it (e.g. do you need to delegate the project to someone else or cancel it altogether if you can't re-activate it). No next actions need to go against anything on hold.
- Someday Maybe
- You've not got any commitment to do or finish the project, so it's entirely up to you whether you feel like you want to start / keep going on the project. You'll be able to decide this in the weekly review. No next actions need to go against anything which is in someday maybe.
"On Hold" is a third option that David Allen only recently conceded, so really, the fewest lists to keep are just two:
- Projects which are active (commonly referred to as just the "projects list")
- Projects which are inactive (usually referred to as "someday maybe").
Even keeping just those two lists will make a huge difference.
The rest is all to do with how you split those lists out.
For example, you could divide them into "personal" or "professional" areas of focus, or indeed, categories like "health", "finance", "family" etc.
The way you choose to split them out is entirely up to you. My favourite tool is Things 3, because it allows you to group projects by those areas, but also switch them between "active" and "someday" while preserving their place in those areas.
My recommendation would be, try to get by with as few lists as possible, and then expand them into those further categories when you feel like you need to.