Every database approaches this issue differently if they have peer reviewed content in it. Here are some strategies to focus in on the peer reviewed content in a database. (Note: it's a good idea in general to verify that an article you find is peer reviewed even if you use these, as a double check).

• Look for a check box in the advanced search that says "Refereed" or "Peer reviewed." Sometimes you'll see the option listed as 'Scholarly' in some way shape or form. *IMPORTANT* Scholarly does not necessarily mean peer reviewed. Using an option like this can help you get closer to peer reviewed materials, but it doesn't guarantee that what you've found is peer reviewed.
• Look under document or publication type. Sometimes they'll have a 'Peer reviewed article' or some variation of name as a type that you can select. 

These are the 2 main ways that databases allow you to limit to peer reviewed materials. If you don't see something like that, it's possible that it's not an option in the database you're using, or the content in that database is either all peer reviewed or none of it is peer reviewed.

Thomas Claveirole

Sometimes you either have to use a database where they don't have an option, the existing option is ambiguous. So what do you do in that case?   It requires a little investigation, but there are ways that you can find out if an article is Peer Reviewed

1. You can try using Ulrich's. A search by title for the journal in which your article is published can reveal if the journal uses peer review. If it is, there will be a little referee's jersey beside the entry in your search results.
2. Cabell's Directory! You can look up the journal in Cabell's Directory and it well tell you about the review process if any.
3. Look at the Journal's home page. You can usually find this by doing a simple web search for the journal title. Look for an editorial board, and instructions to submitters. Instructions will usually tell authors what will happen to their submitted articles (ie, it will be sent out for review).