ALWAYS limit your search to the date range relevant to your topic.
Try searching terms, phrases, etc. that were commonly used at the time in relation to your topic. For example: For World War I, try "Great War" or simply "World War." Parentheses around phrases such as Great War will produce better results.
Look for document-type limiters that may improve your results, such as article, commentary, editorial, front page / cover story, letter to the editor, etc.
This open website from ProQuest features approximately 1,600 curated primary-source documents related to critical people and events in the African American freedom struggle. Documents include historical newspaper articles, pamphlets, diaries, correspondence and more.