Peer review is one of the cornerstones of academic progress, and it's vital that papers are reviewed by a knowledgeable party before they are published, in order to maintain quality. You see lots of advice for authors of papers, but rather less for peer reviewers. If you've been asked to review a paper, here are some tips on how to do a great job and to provide a review which is helpful to the editors and authors.

Get a feel for the field

If you've been asked to perform a peer review, hopefully it is in a field that you are familiar with. However, the paper you are reviewing may be in a different sub-field or use different methods to the ones you that work with. So be prepared to do some research around the topic of the paper, so that you can understand how it fits into the broader literature. If there's an important paper in the field which is not mentioned in the paper, you can suggest that the authors include this reference. Or if a similar issue has been researched in earlier years, you can suggest that the authors mention this previous debate. Make sure you're comfortable with your knowledge of the topic before you start your review.

Check statistical methods, tables, and graphs

One of the most important functions of peer review is checking over the data in the paper – in terms of both how it is analysed and how it is presented. Make sure that you understand the statistical tests which are used, and consider if they are the best ways to test the hypothesis of the paper. If  important data is missing, such as effect sizes, then suggest that this is added in. Also carefully check graphs and tables to make sure that they are correctly labelled and that they are in accordance with the way that the authors have described their data. Are the inferences drawn by the authors in the discussion reasonable, given the data?

Check references

Another important task for peer reviewers is the checking of references. This is something which general readers are unlikely to do, so it's especially important for reviewers to pay attention to. When you see the authors assert a fact and back it up with a reference, go and find the paper being referenced and check whether the authors' summation of it is reasonable. This is also a good time to check whether the references are complete and formatted correctly.

Make your feedback specific and constructive

The best peer reviews are not combative towards the authors, but rather constructive. They provide helpful information on how to make the paper better. The key to helpful feedback is to give specific, actionable suggestion for improvements. So, for a reviewer to say “I find this argument unconvincing” is not very helpful. But a reviewer who writes that “This argument is unconvincing because it does not address this specific important issue, and it would be better to refer to this debate in this context” is much better. Where possible, don't just point out problems with the paper, but also suggest ways in which the paper could be improved.

Follow instructions, and submit on time

Peer reviewing is one of those tasks which everyone agrees is very important, but often gets shoved aside when people are busy. Do read all of the instructions which the editor sends you, and take particular note of the due dates. Returning your reviews on time will be greatly appreciated by the editors and authors and marks you out as a professional. Also, remember to be considerate about confidentiality. You shouldn't discuss the contents of a manuscript or your review of it with anyone outside of the editorial process. And you should not use the ideas in the work you are reviewing in your own papers until the reviewed paper is published.

Be aware of your own biases

Naturally, you'll approach a peer review with your own opinions and perspective, based on your expertise in the field. But you should try to remain as objective as you can when reviewing. Don't reject a paper just because it uses a different method or has a different view from yours, and certainly don't let your personal feelings about the authors cloud your judgement. Be aware of your own biases and try to overcome them to review the work fairly.