I don't have easy access to a scanner, but fortunately it's not really that big a deal.
My biggest thing is that I like to use composable symbols; it helps me know where things are at. (i.e. I can overlay one symbol with another and it will have meaning)
The next most important thing is to keep notes chronologically. It will make it more difficult when you work on a project over multiple days, but it makes life MUCH easier when you're trying to retrace your steps. It's useful to know that you started a project on Wednesday and you didn't get back to it for 2 weeks. It will remind you that there was a big chunk of time in the middle where you didn't touch it.
The easiest symbols are markers for importance, which I just draw a blocky exclamation point for. I use an interrobang if it's an important item that I need an answer for. Anything with a X through it has been completed.
So if I see an interrobang with an X through it, I know to look at the bottom of the page for the answer I denote footnotes with a standard circled number. I've been using the large squared Cahier notebooks, so there usually is only one or two footnotes per page as the Cahiers aren't that big.
I date everything, so instead of writing page numbers, I just write the date that I'm referring to. I don't mind reading a little to get context -- It usually helps me get caught up to read a little extra anyways.
The next item in terms of importance is how I mark my todo lists. I use squares for items I'm going to do, and circles for items I'm expecting someone else to do.
I backslash a square when I start a task and I finalize the cross when I've finished it. If I took the note earlier than today, then I use a star to note that I completed an earlier task.
For tasks that other people take care of, I create the circle when I'm writing down the fact that I expect them to take care of it. I leave a few extra lines of space so I can keep track of any added information, but not too many - I'm big on keeping data in a sequential format, even if it means updates on a specific task are kept across multiple pages. I add hatches to the circle every time I get an update, and when the task is done, I put a big X through it (it's obvious that it's an X to me at least).
Most of the other symbology I use relates to brain mapping type of stuff; I have a symbol to remind me to stop and read a note every time I'm checking the page for something, a symbol to denote that one concept is predicated by another on the same page. Another symbol to denote that a concept is predicated by something on another page, and a third symbol to note that something is in another notebook.
The related symbol looks similar to the carriage return symbol. One line means this page, two lines means this notebook but a different page, and three lines means another notebook. I always mention the date to refer to when using a reference to anything off the page.
Which reminds me, because I keep everything chronologically and not organized by complete documentation, all of my notebooks are cataloged by date. When I was consulting, I put the relevant dates on the top of the notebook (which is why I use the Cahier and not the shiny covered ones) and then the clients that are covered by that notebook at the bottom.
I use right pointing arrows to denote a new set of thoughts or notes (since I will take notes on a bunch of subjects in a single day) and left pointing arrows to remind me that I need to follow up with something.
I use upward pointing arrows to denote "positive" and downward pointing arrows to denote "negative"
I used to use a symbol that would let me know that I was hand-writing something that needed to be typed exactly as I hand wrote it, but now I just use a different style of writing for that stuff because it is easier on the eyes.
Anyways, since this is probably the longest post that I've ever made on this site I'll just say that all of my symbology just kind of grew over time, and I don't know if it would necessarily work for anyone else. My handwriting isn't that great (it's very small and half cursive) so I also contract a lot of words or intentionally drop big parts of words so I can write faster. My focus has always been on being able to keep data as dense as is useful. I could make it more dense than I do now by reverting to a more classical shorthand, but a lot of times I keep track of actual commitments that I've made and that people have made with me, so I've found it best to just try to capture the basic sentiment as closely as possible.
I've tried to keep notes on a laptop, but frankly it's just easier for me to carry my notebook everywhere.
