Have you ever gone into your email to search for something, saw a new important email, and forgot entirely what you were searching for?
Computer usage in general seems to be conducive to doing that. You go to Wikipedia to look up some fact, and suddenly it's two hours later. Ok, you're much more knowledgeable about the Cold War or Ancient Mesopotamia or something, but was that really how you wanted to spend the last two hours?
I've found this to just be something about computers in general: they're such marvelous multi-purpose machines that it's easy to get sucked off one's current objective into something else.
I'm always exploring better ways to work, and a couple years I had an idea of doing "tally marks" as I worked: I would mark down every single action I did. If I was lost or stuck, I would cut down to the simplest possible action, rapidly marking down tallies.
At first I did this on the computer, but eventually I came to a way of working with a notebook and pens right next to me that's been an absolute godsend and marvelous boost.
WHAT I DO

Step 1: On the right side of the page, I write down the list of what I want to do in blue pen.
This is an actual page from a few days ago filled with activities that are easy to understand -- formatting and uploading newsletter issues for The Strategic Review newsletter, writing a future issue, recording receipts of what money I spent, copying down my weightlifting numbers from my temporary log to my permanent one, and then some weekly and monthly planning activities.
I'll typically write out a bunch of things, most of which I want to do.
I generate this list by looking at all the stuff I've got to do that's recorded on my computer: I'll look at Omnifocus (where I keep general to-do's), I'll look at any current project plans, and I'll also just add a few little things that have been bothering me and are on my mind (buy groceries, cut fingernails, do laundry, whatever).
Step 2: As I start working, I write "tally marks" down of actions as I recenter and work.
Every time I shift gears or realize my mind has wandered, I decide what I'm going to do and put down another tally mark.
A tally mark can be as short as a 30-second action. I'm unhesitant to generate a lot of tallies. I'll take notes in real time that say things like, "Feeling confused. Ok, think on very next step." I'll do that for 30 seconds or so, then make another tally mark.
When I get distracted, I'll write "Recenter" or "Reset" and get back to work.
Step 3: When I have new ideas as I work that I want to remember, I'll write them on the right side in green pen.
Basically, both black and blue ink can be thrown away later -- I'm constantly traveling, so I'm constantly purging and throwing away these journals.
It used to be a real hassle to figure out what's actionable. Not any more -- anything in blue or black isn't important and can be tossed.
So instead, when I have a great new idea, I'll write it in green if it's something I want to consider doing and realize later. Anything in green gets copied down to Omnifocus or another durable format later.
Step 4: I cross things out in black when it's complete.
Not pictured in the above image is that I'll draw a gigantic slash through everything once it's not relevant any more. This also applies to when I copy things down in green or red; I'll cross them out with a single line or a gigantic slash when there's no more action. When a page is entirely crossed out, I can tear it out and throw it away, which I tend to do every week or two, or when I'm traveling to a new city.
Step 5: I use red ink to draw attention to critically important things.
I don't use red a lot, but if I have a really critical idea, or I want to go back over a particular session, I'll circle it or put a red star next to it in red ink.
WHAT DOES THIS ACCOMPLISH?
A few things.
1. This generates more "mental RAM."
RAM is of course what your computer uses to load programs. This works like "extra RAM" for my mind.
This lets me know the chain of the next 5-6 things I want to accomplish, without having to keep it in my head.
2. This lets me know what I want to do without checking on my computer.
The computer problem can be ugly... you go to check Wikipedia, and suddenly it's two hours later.
Well, when I work like this, the page is sitting right in front of me for me to recenter. Here's my setup right now in the cafe I'm at in Ikebukuro (Tokyo) working:

So the paper is right there "in my face" even if I get distracted.
3. This generates impetus. Hugely valuable.
"Impetus" is something I think about a lot. Basically, impetus is when you feel an internal pressure to go do something.
The process of seeing the paper in front of me, and crossing things out, generates a lot of impetus.
I won't get into a long theory of what generates impetus today -- maybe another time -- but the mix of having clear set of work to do and the pleasure of seeing tangible achievement by crossing things out both increase impetus.
4. It functions like a really cheap second computer monitor.
A lot of studies show that having a second computer monitor increases productivity.
I can't pack a second computer monitor around with me.
This does similar things: I can use this as a second work space right in front of me.
5. I can draw, sketch, diagram, and do things that are easy to do on paper but time-consuming to do on the computer.
In the first photo, you can see a loosely drawn sketch of a logo with a 'U' and 'W' in a circle. Kai and I are building a new project, and we were discussing potential logos. I drew one way we could do it on paper. Easy and fast.
Additionally, for a lot of tasks like writing, I can either outline on the computer or on paper. Sometimes, when I'm mid-paragraph in writing, I want to stay at that place in the writing in front of me on the computer -- so I'll rapidly outline on paper.
HOW TO DO THIS
The minimum supplies you need are --
1. Any paper.
2. A single pen.
I can do this with a sheet of computer paper, or even just scrap paper that I ask for at a cafe or restaurant, like asking the server for the scrap paper that they use to take written orders on. Almost everywhere has some scrap paper lying around if you ask.
The slightly better version is --
1. A notebook of unlined paper. I prefer unlined paper and feel somewhat more creative on it.
2. Multiple colors of pens. I use black, blue, green, and red. Even two pens -- say, blue and black -- goes a long way for being able to work faster and separate out different types of thinking and ideas.
LET ME KNOW IF YOU TRY THIS
It's more conducive to some types of work and some personality types than others, but it's been a godsend for me. It's hard to say exactly how much more work I do, and how much faster I work, but the answers to both are that it's very significant.
I now actually have "Take out notebook/pens" as the last step of my Morning Routine, and I do this basically every single day before I get to work. It's that big of a boost for me.
So -- let me know if you try this out, I'd love to hear your feedback. If there's a lot of interest, I might do a Youtube video showing how it unfolds over time. If you have any questions, let me know in the comments.
It's been a huge boon for me in terms of productivity -- I've been doing this in some variant for a couple years, and reliably in this particular method for a little more than six months.
It works well -- let me know if it works for you too.
(Oh yeah, and if like this sort of thing and aren't subscribed to The Strategic Review yet, you ought to be. We cover stuff like this.)