How to Peer Review a Scientific Paper: A Guide for Students and Early-Career Scientists

I was a graduate student, new to the publication world, when a mentor asked if I wanted to help review a manuscript. At first, I felt underqualified. Peer review, in my mind, was something reserved for senior scientists, not for someone still figuring out how to format a figure legend. But the experience taught me more about scientific writing than any course I’d taken.

Peer review is part of the hidden curriculum in academia. You know it exists. You know it’s important. But you’re rarely taught how to do it well. And yet, it’s one of the most transformative things you can do as a student or early-career researcher. Reviewing trains your critical thinking, improves your writing, and forces you to think deeply about what makes science clear, fair, and rigorous.

Starting early has its advantages. It pushes you beyond passive reading into active analysis. It helps you recognize flawed logic, vague methods, over-interpreted statistics and by spotting those things in others' work, you’ll learn to avoid them in your own. Reviewing also builds confidence. It’s proof that you belong in the scientific conversation. If you want to understand how good science gets better, start by helping someone else improve theirs.

There are a few ways to begin. One of the best is to co-review a manuscript with your advisor or PI. This gives you a chance to write your own comments, compare them with your mentor’s, and understand what journals and editors expect. You can also make yourself visible to journals by creating a profile on Publons or ORCID, adding your research areas, and signaling your interest to editors. If you’re working in a specific field, consider emailing journal editors with a short introduction and a summary of your expertise. And many professional societies offer peer review training for students and early-career researchers (like this one: https://editingservices.lww.com/peer-reviewer-training-course/).

Once you’re asked to review, the next question becomes: how do you structure a review? Editors and authors generally appreciate a clear, professional, and respectful tone. Start with a brief summary of the paper in your own words. This shows that you understood the manuscript and are engaging in good faith. Then, present your comments in two broad sections: major and minor. Major comments focus on high-level issues like flaws in methodology, statistical analysis, or unsupported conclusions. These are the things that might require the authors to collect more data, revise key arguments, or restructure the paper. Minor comments can include unclear sentences, inconsistencies in figures or tables, and smaller points of confusion. Some journals also invite confidential comments to the editor, use this space carefully, such as to flag ethical concerns or discuss sensitive issues not appropriate to share with the authors directly. It helps editors decide on a path forward, especially if there is a split decision on accept/reject for the manuscript.

One of the most important things you can do as a reviewer is to make your feedback constructive and actionable. Imagine the authors trying to revise the paper based on your suggestions. Can they understand what you’re asking? Could they reasonably address it? Instead of saying “this is confusing,” say “consider clarifying what you mean by ‘physiological resilience,’ perhaps by including a working definition.” Instead of “statistics are wrong,” say “you may want to use linear mixed models here to account for more variables.” The goal is not to prove your intelligence, but ratherto help improve the science. Be reviewer 1, not 2.

Of course, even well-meaning reviewers can stumble. Common mistakes include obsessing over grammar while ignoring major conceptual flaws, making vague suggestions without context, or letting personal opinions influence objectivity. Be cautious about unconscious bias, especially if you're reviewing work that challenges established ideas or comes from unfamiliar institutions. And always disclose any potential conflicts of interest.

One of the surprising gifts of peer review is how much it sharpens your own work. By reviewing others, you begin to see patterns. You recognize when a paper lacks a clear hypothesis, when a method section buries critical details, or when conclusions drift beyond what the data can support. Many reviewers keep private notes after each review: a log of what they’ve learned, what they’d do differently, and what language they might reuse in their own writing. Reviewing becomes a masterclass in writing by editing someone else’s draft. Finally, it's a check on your skills to see the other peer-reviewers feedback. That's often a missed opportunity for most people since they don't always read them or pay attention.

There are excellent resources available to help you grow as a reviewer. Nature’s Masterclass on peer review is a strong starting point, especially for understanding the broader philosophy. The Web of Science Academy (formerly Publons) offers free courses and badges to track your learning. Elsevier’s Certified Peer Reviewer course is well structured, and the PLOS Peer Review Center includes examples, FAQs, and ethical guidance. Templates from the American Chemical Society and COPE (Committee on Publication Ethics) are also incredibly useful for knowing what to include and how to phrase your comments.

You might also spend some time looking at published reviewer reports. Journals like eLife, F1000Research, and PeerJ publish open peer reviews that can show you how others phrase feedback and engage with authors. It’s a behind-the-scenes look at what real scientific dialogue looks like.

As science evolves, so does peer review. More journals are experimenting with open review, where comments and reviewer names are published alongside the article. Others are trialing post-publication peer review or inviting community feedback on preprints. AI tools may help with technical screening in the future, but thoughtful peer review—reading closely, asking good questions, giving clear advice—still relies on human insight.

So if you’ve ever hesitated, wondering if you're ready to review: you are. Not because you know everything, but because you care about good science. You can start by co-reviewing, by reading guidance, by practicing on class papers. But the best way to learn how to review is simply to begin. Pull up a draft. Take notes. Ask yourself: does the evidence support the claim? Is the logic clear? Is the science sound?

Then start typing. “This study investigates…”

And just like that, you’re on your way.

If you're a student or early-career researcher looking for opportunities to review, or a mentor interested in helping someone get started, drop a comment or reach out. I’m happy to share resources, recommend courses, or connect you with journals that welcome new voices.