The One benefit to blogging is the ability to delete before you publish,it is easier to pick any topic, if you start writing something you don't like or decide it isn't really what you want to blog about at the moment then you just delete and go play with your next potential topic. I consider it "play" because when you play there is always a margin for mistakes, whereas with work there is not, besides blogging is fun.
When you think you have your topic and still think you need more ideas the check out other bloggers comments on the issue and comment on their blogs. If you happen across a blog that you fell needs a comment but has nothing to do with your topic go ahead and leave that comment, it may help you with something else at a later moment. Happy blogging!