I don't really have a set thing I go by. I think it really depends on my mood and what has been on my mind during the time. Sometimes I've read something recently that struck me in some way that I felt like writing about it or for other articles it's been about a personal experience I thought may be helpful to someone else & possibly for me too.
There have been times when I've seen a topic discussed in the forums where people say what they'd like to read about that has given me ideas! I love reading everyone's thoughts there, but usually I have a hard time just pulling a topic from the list.
I end up going on some unexpected route every single time! Lol.
Never done the subjective or project articles.