I’m not a blogging determinist. That is, I don’t see blogs as hammers and all problems as nails. But blogs are the best way, so far, to provide updates on what you’re doing and why.
You may well have another, professional blog devoted to your vocation or work life. You may want to blog only in one place, mixing the professional and personal. These are individual decisions and depend on how you work and whether you want to mix the personal with everything else in a deep way.
It’s even possible that you might want to create a purely personal blog somewhere other than your home-base site, if you’re worried that people might misunderstand who you are based on its contents. If you feel the need for that kind of content segregation, consider whether to make that other blog pseudonymous (something I don’t recommend but that is sometimes necessary).
What you blog on your home site is less relevant than the way you do it. If you post items full of misspellings and grammatical errors, people will notice. Taking care matters. If your posts are tedious and self-centered, people will notice that, too. Self-awareness also matters.
As noted earlier, your update frequency is up to you. The only rule that matters: Do what feels right to you.
When I comment at someone else’s site, especially if I’m challenging what they’ve said about me or my work, I try to post an item about it on my own blog. This works both ways. I’ve been embroiled in a few major disputes over the years, and when that happens I make sure to talk about the issues on my own site, and to point back to my own thoughts from the comments elsewhere.
I strongly encourage opening your blog to comments. It’s possible that no one will ever comment, but if you don’t give people the opportunity to respond you are telling them you’re not really interested in what they have to say. That defeats the conversational nature of media and can reflect poorly on you.
Most blogging software and services give you options for handling comments. I’ve set mine up so that I have to personally approve the first posting by anyone commenting for the first time; after that, they’re free to post. I also use anti-spam add-ons to my blogs, because the spammers love to pollute blog comments the way they try to ruin everything else they touch.