Spaced Repetition means revising something after regular intervals. 

If you read something and do not revise it afterward, you will surely forget it. 

To remember things for a longer duration you should keep revising the topics as follows-:

After you finish a topic, revise it just after reading it. Then revise it in the gaps of 1 day, 7 days, 16 days and 35 days. 

This will help you to retain information for a longer time. Also, when you are revising use the active recall method, which will boost your memory skills even more!

The Feynman Technique works on your understanding of things. If you can't explain it in simple language, you don't understand it yourself. 

How to apply it to studies?

 It is simple, explain it to your friends, your pet, your wall, etc. OR, Write down the topic on paper and write everything that you know of it. Now examine all that you missed.

Explain it as you are explaining to a child, in the simplest language. It will also help you to actively recall things.

Think like a child, what all questions he/she could ask and how would you explain them! This will make you conceptually stronger!

In one of my ideas written earlier, I have explained why you should not memorize and rather understand, using Pareto's Principle. 

In learning something new, it's obvious that you will have to utilize your energy. 

If you utilize it in memorizing, you will only be able to answer factual or formula-based questions, not conceptual ones.

But if you understand what you read, first, there is no need to memorize it and second, all the facts and formulas will already be understood, which makes your work easier.

You can check your understanding by using the Feynman Technique!

Pareto's Principle

Whatever you read, try to relate it with your real life. It makes it easier to remember. 

For example, What happens when you keep a cold water bottle outside at room temperature, the answer is simple, we observe droplets of water forming on the surface of the bottle. Was there a need to memorize this? NO. Because it keeps happening in everyday life and you know it. 

That is how knowing real-life application could help you remember things, because -

1. It creates curiosity and develops an interest.
2. It could answer your question "WHY ARE WE STUDYING THIS", which makes the subject more meaningful.