Some thoughts on how to avoid bad blogging:
1. Don't talk about what you're going to talk about. Just talk about it. Is it just me, or does anyone else become extremely annoyed when they get posts on their feed reader that talk about what the blog is about and what its purpose is. That shouldn't have to be said. If you're doing something, you don't need to point out what your doing because your doing it and therefore it isn't necessary to point it out. A good blog title (or subtitle) serves the same purpose.
2. Don't self-promote your blog in your posts. If your posts are good, they promote themselves. There's one particular blog on which half the posts are about how great the blog is. No blog that spends half its posts talking about how great it is can possibly be a good blog.
3. Don't be boring. I think there are some bloggers who think they absolutely must blog every day, content be damned. If you can't write an interesting post on Tuesday, then just hang it up until Thursday when you've got something interesting to say.
4. Don't post images (particularly large ones) unless they are directly relevant (and necessary) to the post. If you've got an exclusive image of the first giant squid ever captured, that's one thing, but otherwise, fugget aboud it.
5. Don't post too much. Some blogs just simply have too many posts. If they were all interesting, that would be one thing, but if there are 5 to 10 posts a day on the blog I can't imagine how they could all be interesting. You just finally get tired of hitting the "mark post as read" button on your feed reader and you unsubscribe.
6. Don't post too little. If you seldom post to your blog, then people finally stop checking and your blog is forgotten.
7. Don't write cryptic or uninformative titles. Titles should do several things: 1. Be complete: They need to describe what is in the post is about as fully but succinctly as possible; 2. Be provocative: the post must give the reader a reason to visit the blog; 3. Be clever: This isn't always possible, but a well-written and clever title tells the reader that the post is likely to share the same characteristics. With the advent of the feed reader, titles have become much more important. Often, I judge whether I'm going to read the post solely on the basis of the title. Some readers only list the headline, so that may be all the reader sees--and the only determinant of whether the user actually reads it.
8. Don't be superfluous. Some blogs try to do what too many other blogs already do. It serves no purpose, for example to be the first to break a story, unless 1. It's an important story, and 2. You're really the first one to break it. With very few exceptions, this is not possible for a blog. The vast majority of bloggers have no business trying to tell their readers something new. Instead, they should be about something else, like telling readers something interesting, or unusual, or edifying, or outrageous, or humorous.
9. Don't try to be funny if you aren't. Humor is like poetry: it's either very good or very bad. The worst kind of post is one that the blogger thinks is funny but the reader doesn't.
10. Don't write posts that are too long. I violate this one too much myself, partly because I use my blog to write drafts of articles and try ideas out. But bloggers who have other objectives need to keep their posts short. A blog post almost can't be too short. I realized one day that the ideal blog post was the kind of thing I used to read in "The Week" section of National Review magazine years ago. It was a series of short, pithy observations on current events. Some were profound, some were very funny, but they were all witty and amusing. Most of them had great punch lines. I now consciously try to aim for this kind of post (with variable success). Blog posts should either focus on one point or be in the form of a list. If you do write longer articles they should have two or three clear points related to a theme or unified with some central metaphor.
11. Don't publish incomplete thoughts. If you want your blog to have a decent readership, and are not just using it for personal experimental purposes, your posts, unless they are very, very short, need to have a beginning, a middle, and an end. They need to be crafted. There's just too much raw information on the Internet. The only thing that is going to stand out is writing that does something interesting with that raw information.
12. Don't write badly. This is perhaps an obvious one, but it is often ignored. Not only should there be an art evident in what you say and how you say it, it ought to follow the standard rules for grammar, spelling, and punctuation. Otherwise, it simply looks careless, ignorant, or, worse, affected. Commas ought to be where commas ought to be, and variant spellings are not very entertaining, except in dialogue. Words that should be capitalized should be capitalized, and words that should not be capitalized should not be capitalized--especially for purposes of emphasis. We don't have typewriters anymore, and have italics ready at hand for that purpose. The AP Style Guide was created for a purpose. Use it.