The best approach to answering a question on literary evidence, which is one of the most common types of sources when studying history, is to use P.E.E. - Point, Example, Explanation. This is the most effective way of answering the question, and it means that you won't begin to write irrelevant comments. The first thing you should do is read the source all the way through, highlighting any aspects that really stand out to you so that they're easier to find when you go back to the source. Then you should start your answer by stating your point about the text (using the Who, What, When, Why, and How approach explained in the next paragraph). You should then choose a quote or an aspect of the evidence that best supports the point that you are making. You will gain more marks if you choose something that is direcetly related to your point, rather than something that is vaguely linked. Finally, explain how this evidence supports your point and the reasoning for why it has been included in the source and its significance as a source.
Another thing you should always bear in mind are these questions: Who, What, When, Why, and How. Who wrote the source that you're reading - how does this change the meaning of the text? What is the source actually saying - is this different to any background information that you might know or does it contradict any other sources? When was it written - does the writer have the benefit of hindsight they wrote this source, and is it contemporaneous to the events or topic of the subject matter? Why is the author writing the source - do they have a motive, and how does writing the source benefit them? Finally, how is the evidence presented - is the source in the format of a poster or a pamphlet, and what does this formatting add to our understanding of the source.