As James Harner writes, “[G]ood annotations accurately and incisively—but not cryptically—distill the essence of works” and “focus the reader’s attention on major points” (28).
Harner, James. On Compiling an Annotated Bibliography. Modern Language Association of America, 2000.
An annotated bibliography is just your standard list of citations, but each source is followed by a paragraph (or more) of critical commentary (the annotation). Annotations must do more than provide a summary! You're basically justifying that source's place among your research. What are you getting out of the source? What's missing from it? Why is the author worth paying attention to?
Your annotation for each source could include:
For (a long, 2-paragraph) example,
Santino, Jack. “Halloween in America: Contemporary Customs and Performances.” Western Folklore, vol. 42, no. 1, 1983, pp. 1–20. JSTOR, www.jstor.org/stable/1499461.
Santino is a PhD folklorist and professor of popular culture, and one of the most prevalent authors of articles studying Halloween practices. In this article, he examines how people “decorate” both themselves and their homes, placing the practices in a historical context, particularly the supernatural creatures and motifs that are part of the holiday. Most of the article is dedicated to an overview of old practices of the ancient Celts and the harvest, with a focus on transformation: figures that do not fit into the Christian heaven-or-hell dichotomy neatly and people’s perception of nature and the wild. Santino connects this to modern times with the pilgrimage people make from the urban to the rural to select pumpkins, corn, and other harvest motifs to bring back to decorate their individual homes – individual ritual for public performance. He briefly compares Halloween to Christmas, another holiday which involves bringing a piece of nature into the home to be transformed: pumpkins into jack-o-lanterns, pine trees into decorated Christmas trees.
This article does provide a useful overview of the development of the holiday into the form we know it today, particularly in the more distant periods of history, which gives valuable historical context to my examination and additional avenues of research thanks to its breadth of topics. However, it does seem unfocused at times, and there’s an uneven treatment of subjects. Much time is spent on mythology of faeries, Fomorians, the Christianization of the Celts, and wandering lanterns, but the adoption of the holiday in the United States from the 19th century Irish immigrants is left undetailed. There are also some seemingly out-of-place mentions of the commercialization (or lack thereof) of the holiday, which is outdated anyway, nearly 40 years after this article’s publication which have seen Halloween grow to a multi-billion-dollar industry.
An annotated bibliography is a works cited list, but each citation for your sources is followed by a paragraph of explanation and justification: why is this source one of your sources? What does it bring to your research?
You will summarize the relevant information you're getting from that source (but remember, this isn't your paper -- you are summarizing, not presenting all the information itself) as well as how this well help you in your research (by providing background information, by exploring a certain angle, by presenting a contrary idea...).
Creating an annotated bibliography is not simply an academic exercise. An annotated bibliography is a tool to help you summarize your source content and evaluate its place within your research. If a source satisfies your "usefulness" criteria, that source belongs on your annotated bibliography. This process begins the transition from reading sources to incorporating content (ideas, quotes, paraphrasing) into your work. It is time to "make sense" of the knowledge you have gained from your research. This knowledge is the foundation on which to build your own voice, explain your methodology, discuss your conclusions, make and report on your new knowledge.
Of course, evaluation of sources goes beyond "usefulness" to the other elements of authority, credibility, currency, and purpose.