It's important to be able to describe - and give examples of the sources of constitutional law. While Britain doesn't have a single document (though life for US Law students is little easier - they still need to remember the key cases; and the law - created under the authority of the Constitution- which governs the workings and relationships of the institutions - and the rights of citizens).
Below is yet another MindMap - again a useful starting point - either for an extended single map - or for new maps specific to the headings of this Master MindMap.
Definitions are again important - don't forget the classic definition of a "convention" - "rules of constitutional behaviour which are CONSIDERED TO BE BINDING by and upon those who operate the Constitution (the Monarch; Ministers; MPs & Peers; judges...) but which are NOT ENFORCED BY THE LAW COURTS"
Examples and legal authorities are important too (the quote above comes from Marshall & Moodie). A review of constitutional history can be a useful preparation for a constitutional law exam!