What's the best way to approach source-based questions?

Source-based questions can be tricky. More than any other question format, examiners choose source-based questions to prevent candidates from simply regurgitating a pre-formed essay. In other words - they force you to think!

ANNOTATION

Before reading the sources, look at the question. With the question in mind, go over each of the sources and consider the ways in which extracts from the source either support the question-statement, or challenge it. If they challenge it, what other factor-explanations might they support? Underline the pithiest quotations that summarise the point as neatly as possible, and then in the margins label which factor-explanation they support. This is key, as when you are writing your essay in a hurry it will be easier to quickly find the quotation you are looking for. At the same time, mark in the margins any contextual information drawn from your own knowledge that would be relevant to the source's usefulness (e.g. reliability, bias of source etc.). 

STRUCTURE

Try and structure the order in which you present the factor-explanations logically. It doesn't matter whether you start with supporting or opposing factors, but it does matter that the reader understands why you are making each point when you make it. Often different factors will be connected - one gave rise to another, for example - and in this case make sure that you order them next to each other to be able to explain that connection easily. For A-Level exams, not every factor-explanation needs to be supported by a quotation from the sources (it could be one from your memory), but every relevant source should be quoted from in the essay!