Robert Bjork, professor of psychology, director of UCLA Learning and Forgetting Lab:

• study, practice several related things at once, not just one thing in one focused block at a time
• learn at different locations
• space repetition, reviewing – f.ex, don’t necessarily take notes in class, rather right after

from geekdad.com/2014/01/everything-about-learning/
(my emphasis)

Taking notes during class? Topic-focused study? A consistent learning environment? All are exactly opposite of the best strategies for learning.
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I recently had the good fortune to interview Robert Bjork, the director of the UCLA Learning and Forgetting Lab, a distinguished professor of psychology, and a massively renowned expert on packing things in your brain in a way that keeps them from leaking out.
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“People tend to try to learn in blocks,” Bjork said. “Mastering one thing before moving on to the next.”

Instead of doing that Bjork recommends interleaving.
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Instead of making an appreciable leap forward with your serving ability after a session of focused practice, interleaving forces you to make nearly imperceptible steps forward with many skills. But over time, the sum of these small steps is much greater
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“If information is studied so that it can be interpreted in relation to other things in memory, learning is much more powerful,”
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Make sure the mini skills you interleave are related in some higher-order way.

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Bjork recommends varying your study location.

…. the spacing effect …. If you study, wait, and then study again, the longer the wait, the more you’ll have learned after this second study session.
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“When we access things from our memory, we do more than reveal it’s there. It’s not like a playback. What we retrieve becomes more retrievable in the future. Provided the retrieval succeeds, the more difficult and involved the retrieval, the more beneficial it is.”
Note that there’s a trick implied by “provided the retrieval succeeds”
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Along these lines, Bjork also recommends taking notes just after class, rather than during—forcing yourself to recall a lecture’s information ismore effective than simply copying it from a blackboard. “Get out of court stenographer mode,” says Bjork. You have to work for it.

side note: i’ve seen recommendation of (and tried) the combination of mindmapping and spacing/ repetition.

from what i’ve tried earlier, and after reading the above, i’d try the following: 

• take notes in form of a mindmap (or at least with plenty of visual notes) right after input (e.g., class or studying)
• take a break and relax for ca 20 minutes, then repeat/ review mindmap
• repeat/ review after a week, then a month
• compile some related topics – create a new, common, less detailed mindmap – and do the same repeat/ review cycle there
• repeat what you want to continue remembering after a quarter, half year, every year (perhaps only the summary mindmaps/ notes then)