How do I find a blog writer ?
Well the first thing that you want to do is figure out what you want your blog to be about. You need to narrow your focus. If you have someone writing on your blog and the focus is too broad, you risk not getting the kind of targeted traffic that you're ultimately going to want to have at some point.
With that said, you can always go to forums of the niche where you're seeking to find a writer. You can also to places like microworkers or odesk that will allow you to post the job that you're seeking to fill.
Ensure that you're as specific as possible about what you're seeking and the level of knowledge that your writer needs to have in order to do what you're going to be asking them to do successfully. Additionally, you should understand that the fees are going to vary widely depending on the writer's experience, the time that will be involved and the quality standard that you're looking for too.