After getting familiar with the GTD (Getting Things Done) ethos a couple years back, I've spent a disturbing amount of time cobbling together systems for capturing, processing and taking action on my stuff. It hurts to think about all the dead end trails, the false starts and the straw men that kept me from fully embracing a system to free up my head once and for all. A huge part of my problem was committing to a system long enough to figure out if it worked. I've been working off of my current system for a couple months now, and feel more confident with it every day, so I feel like I can document it online without inadvertently sending someone else down a frustrating path.
I use a few technologies to capture ideas, depending on what I want to do with it.
Ideas the require action = OmniFocus
I've given several GTD programs test drives, and I end up coming back to OmniFocus. After reading many positive reviews on Things, I tried moved everything over to it and tried it for a few weeks. But it just didn't work with the way I think. I think it projects and sub-projects, which is how you structure OmniFocus. Things relies on tagging, which is a simple concept but doesn't map well to my mind. It was also difficult to get the perspectives I wanted on my actions.
I also use OmniFocus on my iPod touch to capture an action when I'm away from my computer.
Ideas that I can flesh out right now = Evernote
In the past, I've used hierarchical lists or individual text files for this. The problem with that is that I have to think about what to name the files and where they should go, or I get one huge file that seems a unwieldy really fast. I tried OmniOutliner for w while for this, and it worked reasonably well, but I ended up spending way to much time structuring it. Evernote lets me start fleshing something out immediately, and I don't think about where it should belong, since the search works so fast. Since it's got some rich text, I can still do some hierarchical lists when I need to, or I can just stream-of-consciousness it.
Like OmniFocus, I use the iPhone version of Evernote when I'm out and about. For example, the other night I went out on a date with my wife and I kept running into little things I wanted to remember. I kept a new note open in Evernote and jotted things down with my one hand. Call me corny, but the iPod touch is perfect because you don't have to kill the mood by withdrawing your hand from your significant other's to take a note.
Stuff that might be useful or entertaining to someone else = Ecto and Twitter
If the item I want to share is quick, I tweet it. If it's going to take some time, I create a placeholder for a blog entry in Ecto. If I have time, I might write the entry immediately, but if I want to put a pin in it for later I'll just add a descriptive title and maybe a little brain-dump for the text. This blog entry is an example of one of those.
Working out stuff on the inside = Journal.txt
While it isn't often mentioned in the genre of productivity, I think it's worth mentioning that sometimes there are things that you need to think through, things that are bugging you and getting in the way of doing what you really want to do but that are also really hard to put a finger on. I find the best way to work this stuff out is to just start writing, stream-of-consciousness style. I've got a text file so I don't even have to think about formatting, and I just start typing. Without fail, a session with journal.txt leaves me more free and ultimately more productive.
Deciding what to do next
After capturing, the next part of GTD is about deciding what to do and doing it. The idea is that you should be able to re-evaluate your actions on a regular basis so you don't end up wasting time on stuff that doesn't get you closer to where you want to be, and that this evaluation process should be painless, even pleasurable.
Evaluation = OmniFocus
The first thing I will normally do switch to OmniFocus, and review my next actions. I have a list of daily activities which trigger stuff like clearing my e-mail, checking my calendar, petting the cat, that kind of thing. As I go through the process, I might flag certain actions or arrange their due dates to accurately reflect what I want to do.
Execution = OmniFocus or Evernote
The most important part of an effective day for me is having a list of prioritized actions to work from. It allows me to stay focused on stuff instead of continually re-evaluating what I should do next. I'll create this list either by flagging items in OmniFocus, or by creating a bulleted list in Evernote. If I need to think through my priorities, I'll do a stream-of-consciousness on Evernote.
Execution of time-sensitive stuff = Cell phone
My $20 cell phone is the most reliable method for reminders because it's always in my pocket and it works on vibrate mode, so it will alert me even in loud areas. When I add something to my calendar I need to be reminded of, I'll also add an entry to my cell phone. Knowing I have a fail-safe method for timely reminders does a lot for my mental well-being, and it's worth the double-entry.