The following traits often indicate that an article is peer-reviewed:

• A lot of citations: these may appear in-text, and/or as footnotes, endnotes, reference list 
• An Abstract (a 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 the article was submitted and when it was accepted

If you need further help, check out this tutorial on How to Read Scholarly Materials or watch this video on How to Read Scholarly Materials. Just use your DU log-in to view them.