How to Blog?

I have two weeks left at work. Part of me is overjoyed at this thought, the other part is shitting itself. Reason number one being I don't know how to blog. Am I allowed to swear? Be myself? Prim and Proper? This blog will run alongside my business, it needs to be professional doesn't it? I need to be professional? Is that too dull? It will only be successful if I'm professional, right? Oh fuck.