How do I analyse a source for its origin, purpose, values and limitations on History Paper 1?

On History Paper 1, you'll be asked to analyse a number of sources for their "origin, purpose, values and limitations". When done correctly, these questions can be easy points as long as you accurately answer the question. 

The first paragraph of your question should address the "origin" and "purpose" of the source. Read the context provided with the source and use your own contextual knowledge to identify the origin. This should include the date it was written/published, the author or authors and where it was published (for instance, if it was a novel, a newspaper article or cartoon). The purpose, which you should identify in one or two sentences, is the assumed or stated purpose of the source. For a political cartoon, this would be to entertain, saterise and inform. (in the case of a political cartoon, if obvious symbols or images arise, identify them!) A newspaper article, to inform the public. 

Values and limitations should form the majority of your response. Consider the nature of the source but also the facts it contains. At minimum, you should identify at least three values and three limitations. Newspaper articles can be valuable because the journalist would have time to gather facts and consider evidence but can be weakened by being written a larger geographical distance from the event, meaning that the journalist would have less accessto evidence or information. Memoirs contain personal thoughts and emotions which are valuable and not detailed in other sources, but can be limited by forgetfulness or the writers attempt to appear better than they were. 

Be creative with your values and limitations but don't forget to address the obvious values and limitations. (for instance, German sources have a pro-German bias etc.)