While typically advice is to write about you know, I also advise that you write about what you don't know. Meaning if a question comes up where you end up performing a Google search for the answer, why not use the information you learn to write an article about it? If you have are searching for an answer, odds are other people are going to do such a search as well.
Recently, I must have stepped on glass and ended up with a shard of glass buried deep in my foot. While some ways to get glass out of the foot is pretty common sense, I figured I would search for any other methods to remove glass from the foot in case there was anything I wasn't thinking of. After I searched several sites for advice on getting glass out of your foot, I wrote an article on Infobarrel about the various methods and ended up publishing How to Get a Shard of Glass Out of Your Foot. Next time you find yourself searching for the answer to a question online, think about whether other might be performing the same search and write an article to answer the question