DO PRACTICE PROBLEMS and show EVERY mechanism
This.
I took Org 1 and 2 last year and I can ensure you that people who draw every mechanism (without copying it, obv.) for every problem, passed easily both courses.
Going to class just will give you some hints about what subject topics are about. I use books just to cosult what I don't know or what I'm not sure of.
The days which I learnt most are the ones when I'm stuck with a problem and I spend the whole day trying to solve it, consulting books, notes, internet, papers, this forum itself...
Remember, you need TO WRITE IT DOWN, you can't learn O-chem just watching someone or some book solve the problems. Except if you are Woodward, but if you are not you probably can't