An annotated bibliography is an effective way of getting students to not only read the sources for their research essay, but also summarize the most important parts of their sources. I have found that requiring the students to do an annotated bibliography prevents plagiarism because I teach students the difference between paraphrasing and quoting directly when they are composing bibliographic entries. It also helps that I get a chance to see how they are using their sources before they compose the first essay draft. If students create effective entries for each source, they can import this information directly into their body paragraphs. This activity is also a great way to get students to see the relationships among all their sources, which can then help them to integrate multiple sources into a body paragraph rather than just relying upon one or two sources.
If you'd like more information about how to teach students how to write a works cited page and outline their paragraphs, please see my Power Point.