Memorizing techniques
There are different memorizing techniques. The good thing about these techniques - they mix things up. Try to use different techniques now and then, but please remember that you can't build your learning process completely on those techniques. Memorizing techniques are great for learning difficult content or specific topics, but they require time and effort.
Simple mnemonics
The Method of Loci
Rhymes
Using "Rhymes" is another technique for memorizing content. Usually, this technique is being used when teaching children, e.g. in elementary school. Teachers use the format of songs to teach children how to count or how to learn the colours.
A version that might be more suitable for you as a fresh graduate of a secondary school, try to write poetry or raps. It is a nice change to the dull reading and writing summaries. You're not sure if this works?
An example of teaching through rap.
Instructions on how to write a poem.