Helen described the riches to be mined from documents such as inquest reports, obituaries, prison and workhouse registers, divorce proceedings, diaries, newspaper reports, memorial cards, local histories and many more. She explained how a crucial "missing" record containing a date of birth or emigration can often be worked around by locating and then interpreting one of a range of alternative sources.
Analysis of a document begins with its physical format. Is it apparently an original or a copy? Is it printed, handwritten or a combination of the two? Does it carry official endorsements such as stamps or seals? When was it produced? What words are on it? Can you "read" them all? If there are abbreviations, what do they mean? Are there terms with particular meanings that may have changed with time? Is there evidence of being produced at more than one time or by multiple hands? You should be able to produce both a comprehensive description and a complete transcription.
Then consider the source of the information. Was the author personally aware of the facts or merely reporting what he or she had been told? Was it likely that the informant would know the facts as stated? Is it possible that he is relaying reported information? Are there indications that the source has been edited or compiled from other sources? If so, are they adequately cited?
Finally review the context of the document. For whom was it written? Why? Was there a legal obligation to complete it? Was a fee involved? Or a penalty for non-compliance? Who would use the document? Would it be seen by people who would know, and be likely to reveal, if the writer (or the informant) lied? Might the person gain an advantage (or avoid a detriment) by responding in a particular way?
With all of this information, you will be in a position to make a more reliable (but by no means fool-proof) interpretation of the document and extract its treasures.