I think it originally came from the 7 habits of highly effective people.

I'm trying to work this into my to do list, since I problem I have is that my to do list just gets too long.

In Mastering Your Adult ADHD it says to prioritize your list A, B, C and A is stuff you have to do today and tomorrow. Then you complete all A tasks before B and B before C.

The problem with this method is that you only do urgent tasks, but there may be tasks that are important but not urgent.

For example I should go to the dentist. I don't have to go today or tomorrow or even within the next month.... but it sure is important to go to the dentist. With the ABC system I would never schedule it. But with the Urgent / Important system I would hopefully schedule it.

Not quite sure which system to use, or about other options?

Anyone got any preferences?

Here's a Web Worker Daily article about UI NUI UNI NUNI:
http://webworkerdaily.com/2009/05/25/not-a-gtd-disciple-dont-worry-about-it/

Cacho, the best system to use is the one YOU WILL use. Sometimes that is a standard system, sometimes it is a hybrid of a system you like but have tweaked.

In your above example, I would set "Make appointment with Dentist" as an Urgent and let the resulting appointment be non urgent until the day.

I recently ran across an article on Getting Sh*t Done which looked like a good approach to me.

Looks interesting, but I'll have to read more tomorrow... time for bed now.

I've checked into various methods that looked promising and taken what I think would work, or dumped them for the next interesting thing.
It's like a process that is never-ending!

Cacho, the best system to use is the one YOU WILL use.

Thanks. Yeah, that's what I'm looking for. So far this UI, NUI, UNI, NUNI thing makes the most intuitive sense to me. My GF did a big, "WTF are you even talking about!?!?!?" when I tried to explain it to her, so I was wondering if anyone else uses it.

Mine now is a hodgepodge. I used the UI, NUI, UNI, NUNI approach at one time but have eased off of it. The Getting Sh*t Done system works well for me- a checklist of all that needs to be done, check stuff off as it IS done, plan forward the rest. I use red pen to identify the "urgent" stuff- things that HAVE to be done within a standard business day. The list generally is ordered by priority.

What I found for me was that if I spent too much time on the nuts and bolts of a rigid system, I wouldn't use the silly thing at all.