Here's the best principle I've come to understand through research and practicing teaching as it relates to making your study time more effective:
Increasing the number of ways you summarize, interconnect and contextualize information increases both memorization of facts and understanding of relationships and systems using those facts.
The reason for this is both practical (education psychology) and how memory works (neuroscience).
The more ways you have encoded information into memory, the more neural pathways and connections to existing conceptual networks exist, making access and use of that information able to come from many directions. Have you ever had those moments in a test where you just can't remember something and it feels like searching around in your head is like stumbling around in the dark? Yeah well, by having more connections it gives you more ways to grab onto the information - effectively making the distance between where your thoughts are at any given moment smaller.
Aaron Ball. Recovered Academic. Grieving Environmentalist. Evidence-Based Transformational Coach. Electronic musician. Transrationalist.