First, make sure it is an ARTICLE. Not everything that appears in a peer-reviewed journal is an article. Peer-reviewed journals also contain items such as editorials and book reviews, and these are not subjected to the same review process.
Several of the following traits often indicates that an article is peer-reviewed:
- A lot of citations: these may appear in-text, and/or as footnotes, endnotes, reference list
- An Abstract (brief description of the article)
- The organization of the article into sections such as Methodology, Results, and Conclusion
- Charts, tables, or graphs
- Complex, formal language that is specific to the field
- Notes indicating when article was submitted and when it was accepted