A starting point in revision is to identify the key topics that need to be covered. Below is a MindMap illustrating the key parts of the W201 The Individual & the State course.
Once you can visualise the structure of the course - the next task is to draw out the key issues within each major subject. The way that the manuals are structured helps you do that.
For Example - Units One to Five cover "Constitutional Law"
1 Fundamental Values, constitutions and core constitutional principles
2 The sources of the UK Constitution
3&4 Parliamentary supremacy
5 The institutions of State in the UK
Each unit is subdivided - Unit One -
A Identifying fundamental values
B Constitutions: purpose and classification
C Core constitutional principles (1) Parliamentary supremacy (2) Responsible government
D Core constitutional principles (1) The Rule of Law (2) The Separation of Powers
Note the key themes and further divisions - B1, B2, B3.....
You might want to draw your own MindMap for each Subject and/or Unit.
Briefly summarise the key points as you revise - this involves condensing the information.