starting again

I have created a number of "blog" since I started dabbling with them in 2010. I read other people's blogs and I have admired how other teachers have incorporated using them in lessons, but I just never seem to figure it out. What to say, how to set it up, is it right?, is it relevant?... I am taking a class on blended learning and so I start again with a blog. This time it has a purpose.