While working on my PhD I came across a great way to take notes on articles and lectures, and remember the content for future use in writing or exam prep. 

The Cornell system is basically a love letter to your future self: "Dear future self who is about to start writing or studying for an exam, here are the main nuggets of what you've read so far, all clearly laid out and cited. Now all you have to do is organize them. You're welcome." 

Using a specific template (attached), you take your notes in an organized fashion: 

1. The big part is for NOTES: Take raw notes in class or as you read something. 

2. The space at the left is for THOUGHTS: Pull out the important ideas or themes later as you review your notes, or as they occur to you in the moment. This helps solidify the ideas in your memory for the long term. 

3. The space at the bottom is for CONTEXT: Use that for making connections or asking yourself questions like, "How does this fit with that other thing that I read?" or "Make sure to add this to the analysis on that thing from yesterday." 

PRO TIP: Cite the page numbers in your notes as you go! It's easier to pull quotes and ideas from an article from your notes rather than the text itself. Try to ensure you never have to re-visit the article again. When you go back and write, it makes a huge difference to have the direct quotes and ideas in the notes, WITH THE PAGE NUMBERS. That alone will save you hours of drudgery. Treat this as a note to your future self: "Dear future self who is about to start writing, here are the main nuggets all clearly laid out and cited. Now all you have to do is organize them." 

NOTE: I'm told that you'll remember things better if you write them out by longhand, and my experience bore that out. Things I tried to type got lost in my memory, but the things I wrote out (including my notes) stuck with me for the long term. 

Using this approach saved me hours of drudgery, and I hope this helps you too. 

Good luck! 

- MZ 

More details: http://lsc.cornell.edu/study-skills/cornell-note-taking-system/