One idea, applied over and over
Electrons move from where they are abundant to where they are scarce. Nucleophile attacks electrophile. That is essentially the whole subject, and every reaction you are asked to learn is a specific instance of it wearing a different costume.
Memorise the outcome of a reaction and you can answer questions about that reaction. Understand *why the electrons went there* and you can answer questions about reactions you have never seen — which is what the exam will show you, because the examiner knows perfectly well who memorised.
Arrow pushing is the whole skill
- Draw every mechanism by hand, with arrows, from memory. Not reading them. Drawing them. Arrow pushing is a motor skill and it is learned the way motor skills are learned.
- Say what each arrow means out loud — this pair of electrons moves from here to here, because. An arrow you cannot justify is an arrow you copied.
- Predict the product before you look. The generation effect is free and organic chemistry is the ideal place to use it.
- Then do it backwards. Retrosynthesis is where understanding is really tested, because there is nothing to pattern-match against.
What actually needs memorising
A little: reagent names, a handful of specific conditions, some pKa values, the named reactions your course insists on. Card those on a spaced repetition schedule and stop trying to memorise the rest — it will not fit and it does not need to.