• Look for especially intriguing primary sources--ones which, upon close reading, will elicit interesting questions. 
• Identify the type(s) of primary source materials you think you may wish to gather.  Do you want to use images (if so, what kinds?), texts (if so, what kinds?), multimedia (if so, what kinds?). 
• Follow the footnotes in other sources you read; what primary sources are others citing?
• For larger research projects, aim for a variety of primary source materials that will provide multiple perspectives on your topic.  In practice, this means using a variety of search strategies and more than one repository or database.

To start, try searching these Library of Congress subject headings in Primo, then use the facets on the right of the results page to explore different types of materials.

Guantánamo Bay Detention Camp.

Prisoners of war -- Cuba -- Guantánamo Bay Naval Base

The Internet Archive runs the Wayback Machine, which is an archive of over 660 billion snapshots of websites over time.  If the URL to a primary source in your reading no longer works, try plugging it in to the WayBack Machine!

Academic libraries and historical museums often try to digitize primary source collections held in their archives and special collections in order to make them available to the widest possible audience.

The following full-text newspaper databases will let you access local, national, and international news sources.

Advocacy websites are themselves rich collections of primary source material.  You can use the structure of the entire site as a primary source, or select particular elements within it to analyze.  A few examples are listed below: