1. Is the author well qualified as an expert on this topic?
2. Is the author frequently cited by other authorities?
3. Does the author cite the most important research?
4. Do the author's credentials suggest that he or she is a reputable authority on this topic?
5. Do the author's other publications suggest that he or she is a reputable authority on this topic?
6. Is the work current and up to date?
7. Are you using the latest edition?
8. Has the work been published by a reputable printing house or journal?
9. Has the work been favorably or unfavorably reviewed?

For more details, see "Evaluating Sources" in chapter six of The Research Process.