Firstly if it's a technical theory subject:

1. try to learn the concept on which the theory is explained.

2. one the concept is clear, start to study the theory.

3. now just understand it in simple english (or which ever language it is).

4. finally relate it with the concept that you learnt before.

Secondly if it's something related to management or any similar:

1. remember that they are explaining something which happens in real life.

2. read a para or two, try to understand in simple english (or which ever language it is).

3. relate it with some real time scenario.
4. if you really cannot relate it, then at least imagine the situation how it might take place in real life.

Lastly if it's a dry / can't really relate to any thing, then

1. study & understand the content in simple english (or which ever language it is).
2. since you can't relate or imagine, one thing left is write, write, write and practice.

*NOTE: writing and studying is really an amazing way to remember for long term.

Thank you for reading!