Never blog when horny, as the piece will inevitable reduce to soft, or quite possibly hardcore porn.
Never blog when under the influence. People don't need to know about the time you took a crap in those bushes.
Never blog when in the fast lane of a major trunk road, no matter how inspired you might be feeling.
Never blog during sex. You need your hands, and your partner might just respond by stamping on your testicles with those bedroom stilettos you purchased for her.
Assuming you haven't been tied to the bed blogging is permissible afterwards. And if you are tied to the bed and can still blog then I suggest an audition at Britain's Got Talent is in order. I'm certainly impressed.
If you must blog when on the toilet, do take care during those transitional moments. I lost a perfectly good mobile phone this way. The dangers are real.
Never blog if you've nothing to say. Whatever you produce is gonna' be just white sound.
When you blog, remember that a good writer should give the impression he is speaking directly to the reader. Don't waffle, and don't patronize. Be blunt and precise by all means, but don't waste words.
And don't outstay your welcome. People have got better things to do.