As with any other kind of writing, the core advice is all simple. It's putting it into practice that's hard.
You are the reader's slave.
Give good value. Be useful, be entertaining, be engaged. If you're interested in things other than yourself, you'll seem more interesting. The flip side is that if you're only doing a weblog to publicize your work, your audience will be able to tell, and they'll go away. Readers have a magic ability to suss out your motives.
Blogging is like teaching. Mediocre bloggers think the readers are there to pay attention to them. Good ones know they're there to pay attention to the readers.
If you must write about yourself, be concrete and specific, show don't tell, go for stories rather than situations, narrow and sharpen your focus, and keep it as short and snappy as you can without doing damage to the fabric.
If you've got six icky things going on in your life at once, don't whine about them collectively. Pick out one or two telling details that convey the overall situation, and write briefly and interestingly about those.
If you're writing about things other than yourself, make sure they're all interesting. Sure, it's important to do frequent updates; but a missed day or two does far less harm than a boring or insincere post.
Don't write a post about why you haven't been updating your weblog lately, unless the story is compellingly interesting in its own right. The exception to this rule is that you're allowed to explain why,
briefly, if you're well established and have a lot of regular readers.
Allow comments. Respond to comments. If your readers don't think you're listening to them, they won't listen to you.
Regular readers and commenters are golden. Cherish them.
Allow polite criticism. Get used to seeing it as a compliment that someone is taking the time to think about and respond to your writing or your site.
If you're got someone commenting on your site who's more interesting than you are, be grateful. A bit of the gilding is sure to rub off.
If you absolutely put your foot in it on some issue, say so. A forthright admission that you were wrong is almost always going to be an interesting and engaging piece of writing. Also? Your readers almost certainly knew it already. Spare them the strain of being polite to you about it.
Try to always have new stuff up on Monday morning. Most blog reading gets done during business hours.
If you're impressed by an article on another weblog or website, describe what you find interesting about it, and link to it. This is one of the better ways to convince other webloggers that you're worth linking to -- after all, you're perceptive enough to praise their work and link to it. Also, if someone else reads your piece and links to the same article you did, they may well give you a "via" link credit. People who find the linked-to article interesting may click on the link to your site as well, to see if you're interesting too.
If you find an interesting link via someone else's site, credit them when you use it. If they're using
Technorati or
IceRocket or
BlogPulse to monitor links to their site, they may well come have a look at yours.
The reason you should monitor links to your site via Technorati or IceRocket or BlogPulse (or any other sites of that sort) is not to measure your own glory, but to gauge how readers are reacting to the various things you write. Also, it's a good way to find other congenial weblogs.
If you aren't reading other people's weblogs, why should you expect them to read yours?
Unless you're desperate, avoid deals where you link to a blog that'll link to anyone in return for an inbound link to yours. It will make you seem disingenuous and undiscriminating.
Be clear, be readable. Light letters on a dark background are much harder to read than dark letters on a light background. And by "dark letters on a light background," I mean black type in a good standard text face. Poor type choices, color values, and overall contrast will make it wearisome to read your text, but your readers won't perceive it as a design problem. All they'll know is that reading your text makes them feel tired.
Naming weblogs is like naming children. Don't use a name that's twee, coy, embarrassing, unpronounceable, generic, unwieldy, or pompous. While you're at it, don't use a name that suggests that you think you're exceptionally unusual, i.e. weirder than your readers. This is another one of those gaffes that will make them feel like you aren't paying attention.
Very important point: don't use cutesy headlines on your posts. Use a headline that tells what the post is about, ideally within the first 3-6 words. If people are reading you in RSS syndication, that headline is all they're going to see.
The single biggest reason people get the idea that they're not part of some weblog's audience is that the weblog tells them so. If you can avoid doing this, you'll be two or three steps ahead of the game.