WHY SHOULD I BLOG?
Why should I blog? Well here is my insight on why you should be blogging if you haven't started already: the answer is it will bring you more money! Right now blogging is one of the best ways you can organically improve your SEO. Google and other search engines are always changing their algorithms and right now the ones that rank the highest organically are ones that most likely blog the most. More visits to your website= more recognition= more opportunity for sale= more sales= more MONEY.
So, the next question is what do I blog about? Depends... but I think the best way for blogging right now actually is educational purposes. People use search engines to get their questions answered.
Yes you can still blog about your product in service, but the impact it will have to your site may be less. I think having a healthy mixture of both is a great idea. For instance, if I am a photographer I would blog my family sessions, weddings, etc. but also include every now and then a post about your equipment you use; Your first camera from when you started to the one now and why you chose each one in detail. This is just an example but you get the idea.
In the end, blog as much as you can. The more you put in, the more you will get in result.