Some of the basic mechanisms are given in the syllabus
For more explanation and clarification I prefer Clayden's book to study organic chemistry. Mechanisms are the most important thing in organic chemistry. There are lots of books like Peter Sykes, Solomon, Finar. You have to understand the basics first, e.g. Resonance, inductive effect, little bit of ideas of bonding, specially molecular orbital theory and so on. Next, just open a book, take a pen and a copy and start. Teachers say the knowledge in mechanism is proportional directly to the pages you finished practising