When I first started using Remember The Milk, I didn't see the point of tags. Well, I've done a 180 - now I couldn't imagine living without them!

In "Getting Things Done" terminology, there's an "in" box, or universal capture. This is where you write up all your tasks, without necessarily sorting or prioritizing them.

I use untagged tasks for this. I specifically don't tag or prioritize them - I just log them as I think of them. It just takes a moment, because I always have a Remember The Milk tab open, or I can get to it very quickly on my smart phone.

Later, when I have a bit more time, I open up a specific Smart List that I've created in Remember The Milk. It's called Untagged, and the only criteria it has is "isTagged:false".

It might have items I just jotted down quickly, such as:

library
bulb in kitchen
oil change
investments

I then go through these (I try to do it on a daily basis) and assign tags like "home", "errand", "calls", etc. And I also prioritize at this point, and delete tasks I no longer want to do. I might end up with a list like this:

(errand) Pick up books at library
(home) Change burnt-out light bulb in kitchen
(call) Call Acura dealership to schedule oil change
(computer) Review investments on financial website

When my "Untagged" smart list is empty (because the tasks disappear as I assign tags to them), then I know I've got everything sorted.

I even put non-task items on this list (things to buy, books to get, movies to watch, etc), even if they won't eventually go into Remember the Milk, because it's such a convenient universal tool.