One of the most important things to consider when approaching a source based question, is to consider the context of the text. This can be done by thinking 'who, what, when, and where?'
This means that you should be thinking about who has written the source, why they wrote it and what purpose they had. This context can be important in comparing sources.
After considering the context, you should read the texts carefully, and highlight information relevant to the essay question, but also key points that summarize the writer's argument.
Having done this, you should then draw links and comparisons between the sources on things they agree and disagree on. Try to use the context of the sources, and your own knowledge, to account for similarities and differences.
Once you have done this, you can develop an essay plan based on your analysis of the sources. It is important to discuss the sources in comparison with each other, rather than to analyse each source individually in your essay.