What do I need to include in order to answer a 'how valuable' source question effectively?

At A level, there are 3 key elements of these source questions that must be addressed in any answer. These are: 1) content, 2) provenance and 3) tone. Discussing each one in turn: 1) The content of the source is the most straightforward: what information does the source have in it? 2) Provenance is the who, what, when, where and why of the source - who wrote the source, when did they write it, where was it published, why might it have been written? 3) The tone is the feeling that the source conveys: for example, does the writer of the source sound cool and factual? Righteous and angry? The extent to which these three elements make the source 'valuable' depend on the contextual knowledge you have about the period being studied, as well as considering them in relation to each other. For example, if the source is written by someone who was in a position of power during a crisis, and contains a record of that crisis in a factual tone, this gives the source a certain value. If another source you are presented with in the same question contains a different account of that crisis, and is written - for example - by a member of the public, or a member of an opposing faction this also gives it value. When making an argument as to which is more valuable between these two sources, contextual knowledge is vital in choosing one over the other.There are no hard and fast guidelines to judging value. It is to some extent subjective, and what is key is evaluation and argument. Which source is most valuable out of those given? Which is least? Why? Answering these questions by analysing the content, provenance and tone of the sources (though not necessarily all of these for each source) with your contextual knowledge of the period is the key to answering the question well. It is also worth noting that no source is ever entirely without value - if it was, it wouldn't have been included on the exam paper!