My Lists in Remember the Milk generally fall along the lines of where I'd do the task -- not so much an address (where I'd use RTM's "Location" feature), but rather the "Yard" for yardwork, the "Shop" for basement shop projects, and so forth.

This typically works well, as I generally have just a handful of items in each List. But some Lists inevitably end up as "catch-all" lists that contain dozens of Tasks. As an example, a "Laptop" list could contain bills to pay, online items to purchase, articles to read, or emails to write.

For these larger catch-all lists, I want to ensure that each task also has a Tag -- this helps to further subdivide the Tasks into manageable chunks that relate to each other. To make sure this happens, I added an "Untagged" Smart List that shows me any Tasks in these larger lists that don't have a Tag. For me, the definition is simple: isTagged:false (list:Office OR list:Laptop).

Now I can ensure I'm dealing with a manageably-small set of related Tasks, even when the Tasks fall into one of the larger Lists!