1: A clear idea of what you are trying to do
If you want to get and keep an audience for a blog, you need to have a clear idea about a couple of things: what you are writing about, and who for. The word “blog” may derive from “web log”, but if all you do is write a kind of haphazard online diary, only your mother will read it. Don't be fooled by the top bloggers: even though they often seem to be jotting down random thoughts about their day, there is terrific method in their madness – which is why they are top bloggers. Even if they don't articulate it, there is usually a strong underlying theme to their posts. Until you become an A-list blogger, and can do it reflexively, you need to think about what you are trying to say, and to whom, all the time.
2: Strong, interesting and consistent opinions
Having a clear idea of what you are trying to do is not enough: unless you have something interesting to contribute on the subject, people who visit your blog once will not return. The good news is that it doesn't really matter what your opinions are, provided they are strong, well-expressed – and consistent. People like to have a mental image of what a blog is doing, and where it fits in the blogosphere: once you've established a certain tone or approach, don't keeping changing it. It will only confuse your readers, who will get annoyed and move on.
3: The ability to think fast
This is related to the previous point. You not only need strong opinions, you need to be able to form them quickly. Blogs are not the right medium if you want to ruminate deeply about something and then post a 10,000 word essay some months later: time is of the essence (the “log” bit in web log). You need to be able to form snap judgements - but sensible snap judgements, and consistent with your previous posts. Although not crucial, it also helps if you can type fast: the sooner you get your opinion out there, the more likely it is to be a fresh viewpoint for your potential audience.
4: A self-critical attitude
So you've had an idea and typed it up: don't press the Publish button just yet. First of all, read through what you've written: check whether it's clear, and whether you could improve it. In particular, cut out anything unnecessary. People tend to skim through blogs, so you've got to make it as quick to read as possible. Once you've checked the whole thing (good grammar and correct spelling are not obligatory – blogs are informal, after all – but they do make it easier for visitors) ask yourself one final question: is it worth posting this? One of the hardest things to learn when blogging is the discipline of deleting sub-standard posts. A weak post leaves a bad impression, and lowers someone's opinion of the whole blog. If in any doubt, scrub the post and write another one.
5: Marketing skills
Once you've posted something you're happy with, you need to let the world know. One common misconception among fledgling bloggers is that quality will out – that the world will somehow guess you've written some deeply witty/profound/amazing post and rush to read it. It doesn't work like that. Instead, you need to get out there and sell your story. The first thing to do is to make sure that all the blog search engines know about your posting (an easy way to do this is to sign up with Ping-o-matic). Then you need to start posting on other people's blogs to drive some traffic back to yours.
There are two ways to do this. One is to post on anything about which you have an opinion: most blogs let you include your main blog address as a matter of course. The other is to include in your comment a direct link to one of your posts – only do this if your post is strictly relevant to what you are commenting on. One technique is to use a blog search engine like Technorati to find other blogs that are writing about the subject matter of your post: then visit them to see if you can make a sensible comment with a link back to your own blog. However, use this approach sparingly or your comments may simply not be posted.
6: Self-confidence
Even if you've left plenty of hints around the blogosphere that you've just put up an interesting post, you may well find that there's little activity on your blog. Relatively few people leave comments on blogs (and many of those are just publicising their own postings), so the absence of comments doesn't mean that nobody's visited (see below for a good way of tracking all visitors). But you musn't give up: around 50% of all new bloggers throw in the towel within three months of starting, so if you can last longer than this you're already ahead of the field. Moreover, the longer you keep going, the more posts there will be on your site, and the more interesting material for anyone when they do visit. Rather than viewing all the unvisited posts as waste of effort, consider them as an investment for the future.
7: Thick skin/Self-restraint
After you've waited what can seem an age to get a few comments on your posts, you may be disappointed to find that some of them are, shall we say, less than complimentary. It is a sad fact that among those most likely to take the time and trouble to write a comment on your posts are people who feel strongly that you are a complete idiot. Assuming their post is not libellous or obscene (in which case, just delete it) the best thing to do is to reply as sensibly as possible. Do not return in kind, do not retaliate, do not mock: if you descend to their level, you just look as stupid as them. If, on the other hand, you are seen to be responding in a mature and intelligent fashion, visitors will value your blog all the more highly because they will attribute those same characteristics to the rest of your site.
8: Stamina
If you are serious about blogging, you are making a major, long-term commitment. At the beginning, you will need stamina (as well as the self-confidence mentioned above) to keep churning out posts even though few seem to be reading them. But it's even worse, later on, as you gradually gain a readership. Because now there is an implicit contract between you and your visitors: they will keep reading you, and give some of their valuable time and attention if – and it's a big “if” – you continue to post. This doesn't mean every day without fail – though that would be ideal – but it does mean several posts a week, every week. Above all, you need to establish a rhythm that visitors can depend on.
9: Humility
One of the most daunting aspects of blogging is that whatever rank you achieve on Technorati or elsewhere, you are only as good as your future posts: if you begin to post less, or start skimping in your posts, you will inevitably lose the readership you have built up so laboriously. This is obviously related to the last point: you will need stamina to keep any position you have earned. But another danger is that as you rise through the blogging ranks you might start to believe in your own importance: after all, the A-list bloggers do indeed wield great power. But that power comes from the readers, and as soon as arrogance starts to creep into posts, that audience will diminish, and with it the power. It is noticeable how humble many of the top bloggers are towards their audience, constantly thanking them for their attention and loyalty.
10: A day job
Don't delude yourself: you will never make enough money from your blog to give up the day job. Just look at the A-list: almost all of them do something else as well as blog (though quite how they find the time is one of the blogosphere's great mysteries). By all means use Google's AdSense on your site – its online Reports are invaluable, because they give an up-to-the-minute figure for the number of visitors your site has had each day. But as these will show, the sad fact is you are only likely to get one click-through per thousand visitors: even with valuable keywords paying up to a dollar a time, you will need absolutely vast traffic to make a living from this.
Blogging won't ever be your main job, but it might well help you get a better one. The thing to remember about blogs is that they are a great way of marketing yourself to the world – especially the parts you never knew might be interested. This is something else that you need to keep in mind when you write your blog: the fact that at any moment a future employer may be reading it.
(These comments are based on twenty-five years of journalism, including fifteen covering the Net, colliding with a few months of active blogging. Obviously, they are very early thoughts on the matter, based on limited experience. I'd be interested in the views of other people - especially those with more blogging under their belt - on what are the things you need to build up an audience for your blog.)