1. Cast your research net wide! Even if a disaster was local in nature, news stories can often be found coast to coast, or even internationally. Don't stop your research at local newspapers. I found news of the fire in newspapers from New York to Oregon to Louisiana. While many of these papers repeated the same Associated Press story, some papers, such as the New York Times, sent their own reporters to the scene who wrote independent accounts.
2. Look in newspapers for "anniversary" pieces in the years after the event.
3. Check historical societies and libraries near the disaster location to see if the institution has a file or exhibit about the event. If there is a police or fire fighter archive in the area, that, too, might have kept records.
4. Is there a local memorial or monument for the victims or one commemorating the event?
5. Check eBay, book dealers, antique dealers, and Google books for items, books, and papers about the event. Don't forget WorldCat's online library resource.
6. Search for video or film of the event. A few years ago, I found that an online film archive had film footage of the fire.
7. Check court records for lawsuits, plus insurance company files or publications for investigations or settlements.
8. Check government records for investigations or hearings into the event. Did the event give rise to safety or workers' rights legislation? To political repercussions?
9. Search for survivors or their descendants to gather their stories and share those of your family's.