As a reviewer, you represent your community and your review should be professional and constructive. The quality of the venue depends on the quality of reviews. The job of the reviewer is to select high quality, innovative papers for the venue, and to suggest ways to improve the research, as well as to uphold and/or improve on the standards of the community as a whole. For more guidance on the reviewer duties, we also recommend: Alan Jay Smith's The Task of the Referee (IEEE Computer, 4/90)
A persuasive review includes a summary of the strengths and weaknesses of the paper, and the opinion of the reviewer on which weighs more heavily and why. The remainder of this document contains a few pitfalls and recommendations to help guide reviewers to produce constructive and persuasive reviews.
Pitfall: Seek to find all flaws in the paper, in part to show your expertise as a reviewer.
Recommendation: Look for reasons to accept a paper. Despite its flaws, does it point in new directions or expose promising insights? The community can benefit from imperfect, insightful papers.
Pitfall: Since the review process is anonymous, it is appropriate to criticize the paper as if the authors did not have feelings.
Recommendation: Your tone should be the same as if you are giving comments to a colleague face-to-face. It is always possible to be constructive, focus on the work, and do not attack the researchers behind it. The purpose of a review is not only for selecting papers, but to improve the quality of all the work in our area.
Pitfall: Reject papers that build on recently-published new directions, but accept those that build on the established norm.
Recommendation: While truly new papers are best (and rare), consider accepting papers that follow-up on recently-published promising directions. These papers allow the community to explore ideas that can not be fully-developed in one paper.
Pitfall: Advocate rejecting a paper with little comment, because it is obvious that all with agree with you. Ditto for accept.
Recommendation: Explain why you advocate a rejection or acceptance, because people will often disagree with you. Your explanations will make you a more effective advocate or detractor for the paper.
Pitfall: Advocate rejecting (almost) all papers to show about tough you are.
Recommendation: Your job is decide what is best which is not usually accomplished by rejecting every submission.
Pitfall: Advocate rejecting a paper because you seem to remember it being the same as (or similar to) unidentified prior work.
Recommendation: In this situation, the professional should reference important prior work after refreshing one's memory regarding what it contains. One missing reference is usually not a reason to reject a paper.