Summarization is one of the least effective methods of retaining what you have learnt. According to an extensive study [1], the two most effective methods of retaining what you have learnt are
Practice testing --- Self-testing or taking practice tests over to-be-learned material
Distributed practice --- Implementing a schedule of practice that spreads out study activities over time
Practice testing --- Self-testing or taking practice tests over to-be-learned material
Distributed practice --- Implementing a schedule of practice that spreads out study activities over time
http://psi.sagepub.com/content/14/1/4.full.pdf