How to remember

Concentration: Concentration is a limited resource. Actually neuroscientist believe that we remember only a tiny fraction what we think we remember. This happens because we tend to loosen the grip over the text in front of us. The best way to stay councious that we are reading somthing is to write that down. It also helps linking multiple sense organs together and so we can form better associations. This works even if you don’t actually write it down, you can just scribble on paper while in mind speaking exactly what you ought to write.
Take breaks: Don’t try to do it all in one stretch. In many scientific journals it has been proved that 50 minutes of focussed study followed by 10 minutes of absolute refrain is the most optimum pattern for most people. The reason that they give for the same is that when we are not concentrating on any thing (the 10 minutes break) out brain tends to move into the diffused mode of thinking. This is the time when we actually build connections and associations. It is analogous to the hard-disk formating you can not re-format a partition in which you boot up. You need to shutdown and boot in a different partition. You might have experienced it when you could no solve a maths problem even after trying for some hours but once you take a break and then return a fresh, the solution sort of pops-up into your brain. It is also for the same reason that a good nights sleep is important before exam.
Keep it interesting: Don’t consider it a waste of time to form amusing analogies to the text you are reading. The idea is to link the facts with strong emotions. So it can be funny, disgusting, painful, sad, exciting, erotic. As long as it is strong, it is good.
Use Mnemonic techniques: Mnemonics are memory devices that help learners recall larger pieces of information, especially in the form of lists like characteristics, steps, stages, parts, phases, etc. We knew back in 1967 from a study by Gerald R. Miller that mnemonics increased recall. He found that students who regularly used mnemonic devices increased test scores up to 77%!
Many types of mnemonics exist and which type works best is limited only by the imagination of each individual learner. Read more about basic types of mnemonics.
Acronyms : This you probably have been doing since always. Just make sure to keep it interesting and unique enough if you intend to lock it in your LTM (Long Term Memory).
Acoustics: These are phrases / words with no meaning but an interesting sound. The best example of acoustics method is the Major System of remembering a sequence of digits. Here is an article on the same.
Rhyme and Rythm: It is always easier to remembe a song as compared to a prose. Espcially if you have to recall exact words. The reason is that brain identifies patterns. It tends to guess a lot and actually remember only the most important stuff. It is important to narrow down it’s search base while it is making a guess. Agood wayof doing that is to make cosequtive phrases/ sentences rhyme together. You don’t need to be perfect with meter etc. just something that you are sure you would remember.
Say it out loud: This is another way of combining multiple sensory feedback to remember better. Childeren are made to recite the poems aloud for the same reason.
Associations: These are absurd analogies that you biult to remember a fact. eg. if you want to remember tha Hitler was the Chancelor of Germany, You can imgine that there aremany germs in Hitler’s Moustache.
Visualization: Here your imagination has a big role to ply. Try to personify things, conuntries, objects, give them attributes, Focus on the details.A researcher showed two people the same photograph of a face and tells one of them that the guy is a baker and the other that his last name is Baker. A couple of days later, the researcher shows the same two subjects the same photograph and asks for the accompanying word.
The person who was told the man’s profession is much more likely to remember it than the person who was given his surname. Why should that be? Same photograph. Same word. Different amount of remembering due to different approaches of the brain.
Make a story: This method is used to remember a list or even an event. An example of a story for a list is: if you need to remember to get a bananas, bread, eggs, milk, and lettuce from the story, you might make up a story where a banana, a slice of bread, and an egg have to rescue a head of lettuce from a lake of milk. It’s a super silly story, but it has all the elements of your list linked together and will help you remember them.
Make it unique: You can do anything like making some strange noise, doing something foolish, rearranging your desk, do a mimicry of a character etc.
Take notes on the book: If you are reading a pdf there are varoius annotation tools available. With a hard copy you can use a Pencil and a hilighter. It is very useful while revising.
Record yourself: While you speak out loud try to record it onto something. Buy hardware or download a free mobile app. You can listen to this recording later when you are not studying.  It can be played while you are doing something else- Cooking, driving etc. and the best part is you don’t need to focus. This diffused mode of learning will lock things in your brain even while you are not focused on the playback. This also serves as a good way to test yourself. 

Determine what type of learner are you: You need to decide this yourself. For example, some people respond better to audio than visual. Some find it easier to concentrate while listening to music while others tend to slip into daydreaming if they put on music. Also some people prefer to pace up and down while reading, others prefer a comfortable chair. Try not to emulate a friend who you think has better studying habbits or who does better in exams.
Read at least two times: When you start a new chapter, let the first reading be cursory, flip though the pages, look at the pictures, etc. Get a basic idea of what you to epxect from this chapter.
Stay Healthy: As clieched as it may sound, a healthy mind does live in a healthy body. Some of the hormones that help us remember things are also released while doing phycical activities. A streatch followed by a jog or sprint is the best break you acn take.
Eat Right: Sit down at your desk with a full stomach but not quite. Also some foods tend to make us feel drowsy. Try to avoid spices, cheese, and fats. having something to munch is not discouraged but try something better than chips. It can be a carrot or a self made sandwitch. Drink a lot of water and get enough calcium.
Environment: Wear comfortable clothing. Avoid studying in bed or on recliners. Apart for having a negative impact on your eyes it is also a bad association. Remember while studying, something as trivial as scratching your chin can form a tacit association to what you were reading at that time. So it is a good idea to watch your posture and environment especially if you are preparing for an exam in which you would, in all, probability be sitting in a chair. Also keep the desk clean and a pen and paper handy.
Sufficient Sleep: Sleep is incredibly important to improving and maintaining your memory. As hilighted earlier it helps us builds chunks of memory which iin turn helps us recall things.
Test yourself: Keep testing yourself. Do not think of tests as a final thing or a mechanism to quantify how much you have learnt. Tests should be incorparated in the process of learnong itself. Reward youself if you do good. There are certain hormones (like Dopemine) that are released when you reward youself and make you feel confident and help you concentrate better.
Here is a list of TED talks you may find useful-
And some additional resources: