Most scientists acquire their training in manuscript review not through instruction but by actually doing it. Formal training in manuscript analysis is rarely, if ever, provided. Editors usually choose reviewers because of expertise in a given subject area and availability. If an individual repeatedly submits bad reviews, it is likely that that person will not be asked to review a manuscript again. Being invited to review a manuscript is an honor, not only because you are being recognized for your eminence in a particular area of research but also because of the responsibility and service you provide to the journal and scientific community. The purpose of this article is to define how best to peer review an article. We will stipulate several principles of peer review and discuss some of the main elements of a good manuscript review, the basic responsibilities of a reviewer, and the rewards and responsibilities that accompany this process. Proper reviewer conduct is essential for making the peer review process valuable and the journal trustworthy.