Recommended Minimum Weekly Posts by Type:
0.5 diary entry
0.25 op ed
"Diary entry" -- any posts the topic of which is you or something you made. Photos from your trips or of your artwork goes here.
"Pointer" -- any post which is a "look at this cool/interesting/upsetting thing I found out on the internet": links, video embeds, reposts of interesting content.
"Bleg" -- a question put to your readership, such as "what computer should I buy?" or "where should I go when I visit Ulan Blaator?" or "what did you think of the ending of the Sopranos?"
"Op ed" -- "Opinion Editorial": original content by you, but not about you, expressing an opinion you have on something. Reviews and fanfic "meta" fit here, as do more standard opinion pieces.
So let's look at how my blog breaks down ...
Diary Entries: I write occasional "Today's Adventures" posts when we go out and do something interesting. These often overlap with op ed because I tend to review restaurants, movies, fairs, or whatever else it was that we did. If you count Monday Updates, then I'm doing one every week, but those are really just thumbnails. In summer, sometimes I post photo-essays of walks through my yard. I am quite fond of seeing other people's photo-essays in my friends page, and often link to them, but not many folks seem to do them. I rarely read general diary posts. I am intrigued by nature observations such as weather and wildlife. A wide-ranging audience can really broaden your horizons with these.
Pointer: I often post more than three of these per day. I love reading; I love knowledge; I am an information dispensary. I know folks who subscribe to me basically as a newsfeed. \o/ I have at least one person on my friends list who routinely posts link clouds. The only drawback I find here is that it's increasingly hard to find sites that are truly open-access. They often require membership or have limited access, which means I don't want to link to them; I only want to link to things I'm sure people can see. But I absolutely watch for blogs of people who routinely post art, links, fiction, photos, or other things I'll want to pass along.
Bleg: It's not often that I ask a question for personal use, maybe once a month or so. But I do like questions that prompt audience interaction. I recently added intellectual foreplay questions on Thursdays, which is a lot of fun. You may also count the Wednesday round of Hard Things, Good News, and Cuddle Party. I originally instated those to build community, and they do. Most of my op ed pieces also end with some kind of "over to you" question inviting reader discussion.
Op Ed: I post full-blown reviews periodically, probably at least once a month. More often my op ed pieces are long rambles sparked by an article or post that I read. Another thing I do once a month or so is take some list article and comment on every item. Then there are things I write because I'm tired of not having an online reference: much of my Memories list consists of these, which are basically articles. I call those anchor posts. They're reasons to follow a blog, for me -- there are lots of people I follow because periodically they post something brilliant and original.
Other types of content I consider important:
Pictures: I am a huge fan of art and photography on blogs. Why? Something the formula didn't address: the proportion of highs and lows. I don't want everything I post to be tense, and many links are tense because politics is ugly and even science can be depressing. So I look for leavening. Fantasy art, photos of naturescapes, those give everyone's brain a rest. I am especially a fan of tutorials and work-in-progress sets. Similarly, I post some of my photos when I have good ones. Some people have a blog primarily to share their images, which is awesome. To get a reputation for this, you really need to post images at least once a week. They don't all have to be yours; linking to ones you find elsewhere is good too.
Literature: Mine runs to poetry because that's what my fans buy, so it's a large portion of what I post. Some other folks do fanfic or original fiction. This is really a blog category unto itself, as many folks have a blog primarily for their creative writing. I read some of it, not all of it, but my favorites have far outstripped the quality of schlock on bookstore shelves these days. Similarly, you need either a once-a-week minimum, or a less frequent bigger output like my monthly Poetry Fishbowl. Links to pieces with similar flavor can help fill out the other days.
How To: This can be text, images, or both. It generally falls into the op ed category, but is distinctive enough to reference. Some of my photo-essays are things like putting together a Lego kit, instead of walking around the yard. Recipes fit here too, and I post one of those every other month or so. I love seeing this stuff on other people's blogs.
Boosting the Signal: Something else I'm known for is relaying other people's call for prompts, crowdfunding projects, events, or other activities. It's a subtype of pointer, but one that I actively cultivate and which matters a lot in blog culture. This is one of the most useful things you can do to make blogging work and build community. Echo the stuff that other folks are doing. Among the most useful are events like prompt calls, love memes, bingo fests, or the big Dreamwidth activities such as snowflake_challenge or three_weeks_for_dw that actually happen in the blogosphere. However, meatspace events are worth barking up also. This is one of the activities most likely to grow your audience, because people start viewing you as a resource. Ideally, look for other folks who serve as a hub so you can connect with them.
Recurring Posts: These can actually be any of the other categories, they're just something you do once a week or month or whatever. I have monthly posts for all the communities I moderate, because they encourage folks to check in with their activities, and most of the comms also have a regular activity like the monthly bingo fests on allbingo or the Creative Jam in crowdfunding. In my own blog I currently run the Monday Update, Wednesday social posts, and Thursday emotional intimacy questions; plus the Poetry Fishbowl on the first Tuesday of the month. I highly recommend recurring posts for any blog. Ideally, make some of them quick and easy, and at least one with more substance. They give you a framework so you have at least a minimum of content, and they're predictable which encourages people to subscribe if they like that thing. At least one a week is good, especially if you combine that with a bigger monthly one on a different topic.
In general, the most important thing about blogging is simply that you post. Activity is more important than type of content. You need a minimum of one post a week to hold most readers. Once a day is a good target. More than a handful, and some people will drop you for being too busy, but I've only had a handful of folks do that, and I've only dropped a few people for that reason. Don't worry so much about making a post "long enough" or "important enough" or even "good enough." If you blog, you'll get better at it -- especially if you observe popular bloggers to see what they do right.
Your blog will be more effective if you have a goal. You can blog about anything, and while some have a narrow theme, most have a general type with a handful of interests. Mine is pretty heavily a writing blog with a large helping of activism, some very avid cyberspace community building, and enough leavening to keep it from being a buzzkill. Ideally, try to include at least one thing that's widely popular, which will interest many possible readers; and one thing that's more obscure, where you'll have little competition. I post lots of links, because almost everyone loves links and a good linker is highly valued; but I'm also one of the few people writing about characters with disabilities, which has a much smaller but very devoted market. People like all kinds of blogs, the chatty personal ones and the literary ones and the political ones and so forth. Just pick something you enjoy doing.
Regarding audience quality, the rule is this: you get what you permit. If you let people act like assholes, you'll have a troll farm in no time. If you expect people to behave decently, and post your expectations in your profile page, and occasionally step in to moderate heated exchanges, then your blog will be more civil and your audience more genteel. It's okay to have a rantblog if that's what you want -- people need space to vent. I went a little different with mine in making the Hard Things feature, which gives people a contained space to complain about challenges, get moral support, or pat themselves on the back for accomplishments. Some people stumble across my blog on their own, but I also watch for interesting folks in fests, on addme, and in comments in friends' blogs. If you want a bigger, more active audience then those avenues are worth pursuing.
Finally, remember to post on other people's blogs. This builds community and also helps attract new readers to your blog. They see you in a blog they already read, and follow you home. In this regard, it is most useful to comment on high-traffic blogs with a large active audience. You should also comment on close friends' blogs to help maintain the relationship; this is sometimes called social grooming. Another good place is thematic blogs that match your area of expertise, where you can often add valuable content. You'd be surprised how easy it is to get the attention of experts if you can say something useful and interesting.