Questions to ask: What am I interested in finding that I can’t find in secondary sources? Who might have created the materials I’m looking for? When might they have created them? Where would those materials have been created, Why, and for Whom?
Think about the variety of document types that exist in archives (manuscripts, correspondence, diaries, photographs, audiovisual materials, computer files, scrapbooks, meeting minutes, reports, data sets, etc.) and ask yourself how various document types might factor into your research and analysis.
When deciding if an archival collection speaks to your research inquiries, review inventories, finding aids, or collection lists. Talk to an archivist!
Before going to the archives: Do background research to develop specific questions. Some materials (finding aids, digitized collections) may be available online, but not most.