Both Comparative and analystic source questions are difficult to approach if you have not been taught exactly how the exam boards like them answered.
In my experience, there is a relatively simple process that applies to all source-based questions, including questions asking you to compare two sources.
To begin with, you must gather the basic information from each source. When first reading the sources, note down these four things:
Content- what does the source actually say? While it seems simple, the first marks you willl get are from drawing out some of the basic information that is contained in each source. Examples include what events they are talking about, people mentioned and their actions etc. Once you have noted this information down, try and find similarities and differences between the two sources you are comparing.
Context- Next up is context. For this, you must bring in any historical knowledge not in the source to expand your argument. This includes who the author was and where they were from (its provenance), and why it was written (the purpose). Note these down and include any reasons you think the purpose of the source could help explain what is written, e.g. is it intended to persuade people to think in a certain way? Is it intended to distort the truth? Again, after you have looked at both sources, you should note down whether there are significant differences or similarities between the two sources
Significance- Once you have looked at the content and context of the sources, you must bring together what you have found out so far and decide which bits are significant. For example, does the fact that author was writing at the time mean that he or she is a more reliable source? Is the fact that they fought on one side in the conflict they are writing about mean their work contains bias? This is especially important in straight-up analysis questions, however should definitely be used when comparing sources too. At this point in a comparative essay, you should compare the content and context of both sources together, mentioning which is probably more reliable and any other relevant features of the context which help explain what is said in the content.
Cross-reference- This is absolutely vital to gain the highest marks. At this point, you need to cross reference the source you are analysing with all the other sources in the paper to see whether the back up what is said. In a comparative essay, you need to use information from other sources to prove which source is more accurate or reliable, as in these questions, they will often choose sources that show opposing view points. In addition to using the other sources in the paper, you must use your own knowledge to cross-reference what the sources say. This should include relevant dates, facts and statistics that support or oppose what the sources say and help you decide its accuracy and reliablilty. The top band of marks are reserved for those who pick up on the most complex details of the sources and then use their own knowledge to analyse these points further.
To conclude, once you have done these four steps, you should have analysed the source pretty thoroughly and if you can include the most relevant and interesting points and comparisons you discovered, then you should be able to get a solid mark. Remember, these four steps are to be used in the planning stage and you SHOULD NOT structure your argument with a paragraph on each stage. Your actual essay should be structured with the information you gathered at each stage integrated into a well-written argument. Therefore, when analysing sources always remember: Content, Context, Significance, Cross-reference.