Matt Mullenweg, creator of WordPress, starts 2014 with a nice reminder of how to focus your blog writing if you're having trouble keeping new posts flowing:

The antidote I’ve found for this is to write for only two people. First, write for yourself, both your present self whose thinking will be clarified by distilling an idea through writing and editing, and your future self who will be able to look back on these words and be reminded of the context in which they were written.

 Second, write for a single person who you have in mind as the perfect person to read what you write, almost like a letter, even if they never will, or a person who you’re sure will read it because of a connection you have to them (hi Mom!).

Matt's post reminds me of John and Merlin's talk at SXSW '09. Deciding on who you're writing for will go a long way towards informing what you should be writing.