Choice of system, not that important

What system to use? It really does not matter! Anyway, such a question is beyond the scope of this article. When choosing your system remember that ideas don't sit still.

Your capture devices have to record things that occur to you anywhere – shower, while driving, when on the phone, while sailing – any place, any time.
If it has batteries, they will go flat.
Electronic devices fail, and there is no assurance the replacement will be able to read the old files or run the old software, or even that you can get a replacement quickly.
If it uses networking, (WIFI or mobile) you will sometimes be out of range.
The more valuable your device is, the more likely it is that some thief will take it.
I can guarantee that you will lose the system or have it fail at sometime.

Choose your capture devices and locations with care.

If you missed it, read as well part 1 of Ian Hobson'sTime Management Tips We are not well adapted to modern life. As hunter-gatherers, we had impulses and thoughts. These would have led to the discovery of new food sources. We also have a cautious part that would protect us from danger by slamming on the brake if we entered another tribe's territory or suspected a predator is about. Today we are very safe, and the cautious part is over-active. When you have an idea or impulse, act on it within 5 seconds. If you don't your brain will slam on the emergency brake. If you can't act now, capture the idea and review it in your next planning session. (Of course, if the action is to speak to that interesting person getting off the bus, you better act fast, or they will be gone).

Once captured, all new thoughts and existing plans are reviewed on a weekly basis. Collect all thoughts, and inputs from all capture devices (including your diary). Review your goals, and then choose from a small number of fates for each piece of "stuff" you have collected. Stuff will include what is left of last week's plans. Does each project have a "next action" and is the plan for it adequate?

Ask "What's the next action and who does it?"

You know the action, and you are to do it. Add the action to a list of actions for that context. E.g. add "buy AA batteries" to the shopping list. Note – every entry has a verb and a noun. If it has a specific date and time, it goes in your only diary.

Its an action for someone else so you choose to delegate it. (This can be delegation upwards or to a supplier). Set that in motion. Decide the instructions. Add "Do and advise" or "investigate and report" as appropriate. Diary your follow up in case of trouble.

Its actionable, but multiple steps or you don't know what the next action is. So break it down, adding each step to your capture list! Then decide how to handle each one.

It not actionable but you have to keep it for reference. File it.

You are not sure. It needs incubation? Move to a "Sometime maybe" list and review next week.

And the rest? Junk it.

Seriously. Junk it all. Junk more than you are comfortable with. If you have to find the information again, you will find the fresh up to date information. You won't have maintained it nor will you have to check it is still current. If the topic appears in you life later these will be time later to handle it. So you can be ruthless about removing junk.

When working, after completing each action, take a moment to review that project. What next actions can now be accomplished? Add new actions and cross off the action as completed.

What about mistakes? Make them with joy. A boat cannot be steered until it is in motion. Even going the "wrong" way will tell you something. Get in motion, make a start. Don't wait until "it feels right" (It never will) nor until you are ready (that will never happen). Most of what you need to know about something you will not discover until you are deep into it, so you mus start before you are "ready".

Recall that there are 4 activities. Plan, work, rest, play. Your plans must include enough of each!

Finally, as you get busy, you will have more and more demands upon your time. There will come a point when you will have to turn down a lot of requests. Derek Silvers came up with the idea that you must say "Hell Yeah!" or the answer is no. This harks back to good goals jamming themselves into your schedule and pushing out others.

Now I'm off to try and take my own advice!

Notes There is nothing special about 2 minutes. The point is that the trusted system is an overhead. If the action is trivial it is better to do it now and skip the overhead.
David Allen – See http://gettingthingsdone.com
The palest ink is better than the best memory, is probably from the Chinese proverb 好记性不如烂笔头 which actually compares memory to the worst pen nib.
Hell Yes, or no. See https://sivers.org/hellyeah. If you plan for 2 days a week for thinking/planning, then you might achieve one – and that gives you enough time to say "Hell yes" to things you do want to do. After all luck favours the prepared.