There are a number of blogs that are generally about writing a thesis in education. The thesis whisperer is well worth a look.
The important reason for having a blog is that despite your best searching efforts it is unlikely you will find all the folk who might be valuable as part of your network. You can, with a blog, attract them to you!
How you blog, how often and why is a personal style thing for most people. The way the new opportunities are understood by many is in terms of speed, speed of sharing, of getting your ideas published and of finding things. There is an eloquent case that can be made for slow scholarship. So blog become slow blogs or slogs. Tweets become slow tweets or sleets. :)