Depending on the purpose of your bibliography, different elements will be more important and some may not be important at all. Your professor may also have guidelines or be able to talk about specific expectations. In the absence of such guidelines, consider the purpose of your bibliography and then select appropriately from the following elements:
Who is the author? What is her/his background? Is the author qualified to write this document?
What is the author's purpose in writing this article or doing this research? Is the purpose stated or implied? Does the author have a particular message?
To what audience is the author writing (scholars, teachers, the general public, etc.)? Is this reflected in the author's style of writing or presentation?
Does the author show any biases or make assumptions upon which the rationale of the article rests? If so, what are they?
What methods did the author use to obtain the data? Is the article based on personal opinion, experience, interviews, library research, questionnaires, laboratory experiments, empirical observation, or standardized personality tests?
What conclusions does the author draw? Are these conclusions specifically stated or implied?
Are the conclusions justified from the research or experience? Are the conclusions in sync with the original purpose of the research and supported by the data? Are the conclusions skewed by bias?
Relationship to other works
How does this work compare with others cited? Does it conflict with conventional wisdom, established scholarship, government policy, etc.? Are there specific studies or writings cited with which this one agrees or disagrees? Are there any opinions not cited of which readers should be aware? Is the evidence balanced or weighted in favor of a particular perspective?
Is the work current? Is this important? How does the time in which it was written reflect on the information contained in this work?
Are there significant attachments such as appendices, bibliographies, illustrations, etc.? Are they valuable or not? If there are none, should there be?
Each annotation should be clear, thorough, and accurate. The goal of the annotation is to concisely describe and evaluate a source so that other researchers can make a decision about following up on it for their own research.
An evaluative annotation might try to answer these questions:
What does the source set out to do and what does it conclude?
What is important for the reader to know about the method(s) used to arrive at the source’s conclusion?
Who is the audience for the source – what type and level of researcher might find this source useful?
What are the pros and cons of the source’s approach, or how does this affect the conclusions of the work?
What is unique, especially striking, and/or missing in topic coverage in this source?
What bias, if any, can be detected?
Questions? Contact firstname.lastname@example.org