When I speak to people about blogging to increase the visibility of their brand, one of the questions I often hear from them is "what do I write about?" My advice is to take the every day occurrences, the things that come up in the course of your job, and write about them. It doesn't matter if everyone else has written about backing up SQL Server databases, or writing a query to find duplicate rows; it matters if you have written about it. A potential employer often your blog as due diligence on your skills, including the way you communicate information to others through your writing.
However most of us also encounter these seemingly trivial, minor problems that plague our environments. We find creative solutions to the problems, solutions that others might not think of. They don't seem to be worth sharing. I hear so many SQL Server professionals belittle their work, thinking that anyone could build the same solution. That might be true, but for every problem you solve, there are probably others working with SQL Server that would benefit from hearing about your work.
New people come into the SQL Server community all the time. There will be people that connect to SQL Server with Management Studio for the first time and back up a database. This week someone is writing their first T-SQL query and executing it. The trivial, simple solutions that you develop for common problems might just help one of these beginners learn something, and solve a problem their first week as an accidental DBA.
Write about the common things you do. Share the solutions you develop. Pay it forward, since most of us have gotten help already from someone else in the community doing the same thing.