What I hear, taste or smell I register: what I fell, I concretize: what I say I understand. There is no automatic thing anywhere. The one you call automatic is not so because it will still need the assistance of human brain before it operation. Some people cannot simply and easily remember their neighbor's telephone number or address. My friend what of your ATM card pin? Remembrance is not automatic. To remember anything in life you need to keep all your SENSES ALIVE. Don't be deceived, you don't need any herbal medicine nor medical capsule to remember anything. God has arranged your mental system to understand and recap all what you store there.
That what you hear in the classroom make sure you hear it very well. Until it has entered into your mind it can never be remembered.
This involves playing it back, practice it, repeat it aloud, say it over again until it becomes familiar with you.
Reading and studying are not the same. In study you go deeper in paying attention to understand better. Study demands attention than reading. When you research, you diligently inquiry or examination to seek or revise facts, principles, theories, applications, etc. All these improves your remembrance.
In the process of cramming, you question and test weather it has saved inside your mental system and "key" it.
This will help you to sit right and tackle questions. In the process of group discussion you will know quite alright weather you are fit to sit and the subjects you registered for. It is better if you are the ring leader to coordinate the sharing. Apart from helping your remembrance, it will also help you to measure your fitness for approaching examination.
By imagine what you hear or heard allows you to have picture of it in you. Imagination is image formation. It has to take root inside of you. Let it pass through the dark room of your mind called "sub-conscious".