I use the following smart lists, combined with the "Near By" location aware smart list on the main home screen of my android, and a wall of widgets on another home screen with lists 1, 2, 3 and 5.

1) Bucket: for unorganized tasks. To progress: either tag them, give them a due date or a location.
((list:inbox and isRepeating:false and isTagged:false and isLocated:false and not list:"3) Next Actions" and not list:"6) Future"

2) Review: for tasks that i've organized or given a location, but not a due date or or tagged with nextaction. To progress: give them a due date or or tagged with nextaction.
(((list:inbox and isRepeating:false and (isTagged:true or isLocated:true) and not list:"3) Next Actions" and not list:"5) Waiting" and not list:"6) Future"

3) Next Actions: for tasks that I should do. To progress: Complete the task, or change the due date, or remove nextaction.
list:inbox and ((tag:nextaction and not list:"5) Waiting") or not list:"6) Future")

4) Completed: tasks that i've recently completed
4: list:inbox and completedWithin:"1 week of today"

5) Waiting: tasks that are waiting on someone. usually tagged with both "waiting" and a tag for that person. Or maybe whom i'm waiting on in the title. To progress: remove waiting tag.
list:inbox and tag:waiting

6) Future: tasks that don't need to be done for a while (5 days away).
list:inbox and dueAfter:5

Near By: tasks that need to be done, and can be done near where I am.
(list: "3) Next Actions" and locatedWithin:"300m"

Important Tags:
- nextaction (this is the next action, but doesn't have a due date)
- waiting (this is waiting on someone else)

Main Locations:
- home
- office
- supermarket
- parents

I hope this has been useful to some of you. Look forward to any comments/suggestions!