I try not to let my religious or political or 'controvercial parenting' views come into play. Now if the focus of your blog is a religious one, well then that's fine. But for me, these are no nos. Great topic!
I never blog about my friends or their families, lives, etc. At least not by name or location. That's an invasion of privacy, IMO, unless they give me permission to do so. Same with pics- I only post pictures of my immediate family- those who live in my house.
I'm not too adverse to blogging about any topic, because I'm of the mind set that if I say something someone disagrees with, they don't have to read that post, or even my blog if I offend them (which I'm not trying to do at all.)
And definitely no naked pics- I'm too paranoid of all the people looking for them / at them for the wrong reasons!
Just taking a stab at this...I pretty much tell it like it is in my posts, describing in great (and sometimes horrific) detail the mundaneness of my existence here on the planet. But I probably wouldn't reveal anything that could come back to bite me--like disparaging commentary that is specifically directed toward someone I know (unless I have their blessings, that is). Please note: I don't personally know Paris Hilton, Barack Obama, John McCain, George Dub-ya or that looney astronaut who wore diapers and stalked a co-worker as a result of being involved in some ludicrous love triangle. So I went to town on those folks, clickity-clack on the keyboard, handily making sport of them for all the world to imbibe.
As far as other areas of concern, I generally steer clear of handing readers stuff like my phone number, for instance, my street address, my SS#, my recipe for Black Magic Cake and to-die-for marinara sauce (well, maybe not so much the last two). Just let me know if you want the silly things; the cake (and I'm not lying here) is damn near orgasmic. ;-)
As for leaving comments on other bloggers' posts...sarcasm is good...flaming is bad...very baaaaaaaad. :-)
I think Bekkah's fab list applies to me as well. I don't mention trips or anything until after the fact. No naked kiddie pics. In real life, I am a pretty irreverent person, so my blog definitely reflects that, hard as I try to keep things clean...that rarely happens. I do try and keep my strong political views off of it though, but a look at some of my blog roll faves may give that away anyways:)
Well, I try to keep it about me - like some others have posted, I don't blog about politics and religion, unless I have something I am questioning that maybe a reader can answer. I don't post my kids pictures or names, but other than that I play it by ear.
I do blog about religion, but that's because it's a big part of who I am and my readers know that.
I don't blog about politics ever. I don't want to lose readers because we don't share the same opinions. (although it's going to be ROUGH during the presidential election to keep my mouth shut as I volunteer for campaigns. LOL)
I also never post nudity and never post any info about friends or family without their permission.
I do post on religion every Sunday, but that's so central to who I am, I can't avoid it. So I try to keep it to Sundays, so my non-Christian readers know when to expect it and can avoid it if they like.
I try to avoid politics, but I jumped into a book review series that made it hard to avoid politics. It provoked some good discussion though. I think if you're not a political blogger, and you want to post something political, they key is to not do it often and to state your case, but make it clear that you welcome polite discussion, even if people don't agree with you. You'll still get the rogue rude person, but most people will enjoy the discussion.
As far as no-no's, I don't use my kids' real names, I don't mention where they go to school, and I try to keep my location general. I also try to be respectful to readers, even if they're not being respectful to me (rare, but it does happen).
I think another no-no that hasn't been mentioned is going too far off your blog topic. My topic is finances & frugality, and if I started covering entertainment and fashion, my readers would drop me like a hot potato.
First and foremost, I always try to remember that a anyone could be reading. I mean, you never know.
I don't like profanity, so I keep it clean, and like others have mentioned, I don't use their pictures or names unless I know they're ok about it. And I would never write anything that is hurtful to someone else. Once it's out there, you can't take it back.