There’s no one “right” answer to this. It’s all about what helps you A) remember information, and B) look stuff up later.

If underlining or writing marginalia helps you, then go for it (though that makes you a monster). If filling notebooks with longhand is best, do that. If you want to type out a document on phone or computer, then do it!

Personally, what works best for me is digital notetaking in a format that syncs between my phone and computer. (I use Apple’s Notes app, personally, but there are other options!) I take notes with one document per book. Here’s a sample entry from my file “By Sword and Plow,” which contains notes for Sessions, Jennifer E., By Sword and Plow: France and the Conquest of Algeria (Cornell University Press, 2011).

75 Louis-Philippe’s instructions for his son’s education “specified that he be taught that his birth and privileged status were the result of pure accident and ‘that He alone by his actions can prove that he is worthy of them.’”

In it I note the page number, directly quote relevant bits, and paraphrase other important context. Some notes are just a quote, others just a paraphrase, and some (like this) a mix of both.

The important thing is to be disciplined about making sure notes include all relevant key words I might need — referencing important topic names or people so they’ll pop up in a search. For example, I’ve had good luck searching for the word “francs” to find all notes I’ve made about how much various things cost in 19th Century France (as long as I make sure to write “45 francs” instead of “45f”).

Outlining is nice to be able to locate text again, quickly. I don't like dog-earing pages, and adding tabs to them can be helpful only if there are relatively few pages to note. Otherwise, I think I have had the most benefit out of jotting down page number and a few key words, on a notepad document. Later, if the document becomes too big to easily scan by eye, I can use the find feature with a keyword, and go right back to the page I need. If I don't want to highlight the book's pages, I may also note "4th paragraph," or "2/3 way down" or something like that. So if a particular chapter was about Washington Crossing the Delaware, I might note "Pg 228 para 3 Washington Delaware Hessians"

I don't really annotate books (most of what I read is library books, so it's not like I can)- but I make notes: schoolwork with pen and paper, research in a Word document and various other interests in my commonplace book.

Regardless, I tend to jot down the main points, the page number, and various observations, correlations and reminders to check other works on the subject.

With my research work, I tend to copy extracts or sometimes the entire documents when I deal with primary sources, and then to come back to it for analysis once I finish harvesting.

My commonplace book notes are the least rigurous - I tend to mention the source and just resume the information - since it basically contains everything that tickles my fancy, not just history.

I LOVE to annotate. I’m history/secondary Ed majors + American studies minor. I really only annotate my mom-fiction books or historical fiction. I am a person who if it doesn’t immediately catch me, I’ll read and honestly forget everything I just wrote. I’m also taking classes for social studies teaching so that involves everything from philosophy, to history, to even economics. I go to a used bookstore that’s my favorite. And some of my books are from the early 1900s. I have zero shame in writing in them.

Annotated books aren’t to share (IMHO), if you got your hands on someone else’s…. it wouldn’t make sense to you. It’s a very personal experience. It’s like a diary in a sense. I write very personal things, mostly in my philosophy, psychology, and historical fiction. I’d never let anybody read it. Annotations aren’t there for extra work. If you find it work, you’re probably not doing it right for you. It’s really a trial and error to find what’s for YOU.

So honestly what I did is just to grab a pen, or some post it’s, etc. and try it.