As of now, mostly notes from this video:
Barbara will teach a class on that topic on coursera (https://www.coursera.org/learn/learning-how-to-learn) beginning in November.
They activate different neural pathways of your brain. Just brute-forcing a problem in focused mode might not be the most efficient way to attack a problem (you might be stuck in a neural pathway that just cannot understand the problem).
Diffused thinking can also happen subconsciously, when taking a walk, ...
There is anecdotal evidence that Dali and Franklin would sit with a bell in hand, wait to fall asleep. Then the bell would drop on the floor, they would wake up and start working (as a way to work using the 'diffused' neural pathway). Not sure how much weight we can put on those anecdotes.
Use the pomodoro technique: time 25 minutes of focused work, then reward 5-10 minutes of something you like.
Important to reinforce the ability to stay absolutely focused for 25 minutes: if you have distracting thoughts arising, acknowledge them and let them go.
It is also important to not neglect rewarding yourself after successful 25 minutes stretch of work. Procrastination is partially due to switching to something better that feels good right away (instead of the hard that your task feels like). Train yourself to expect good feelings after 25 minutes of focusing.
You build new neurons all the time. Sleep and exercise are important to that processus.
You may feel that you know something, but you do not really know until you are able to recall and apply it. Repetition goes a long way. Do not mindlessly repeat the same thing, switch topics and concepts, but come back to something you learned in the past and do the exercise again, and again... Think about it in the same way as learning a language or to play an instrument -- you would not expect to play something once and master it immediately.
A good way to read is to read a certain amount, close the book and see what you can recall. The process of recalling is where the learning happens.
Use smart cards (spaced repetition, anki) for all topics, not only languages.
It is usually possible to distill complicated principles to 'simple English' that a 10 year old could understand. It may be useful to do that in order bring order and simplicity to a complicate topic.
A good way to learn is to focus on chunks (divide a problem in small concepts that you can understand well). This is useful because our working memory can only hold 4 items at a time. Break down the problems into small chunks that you can really grok, then zoom out and link the chunks together.