One mistake I see new bloggers make is to start off by writing 20 posts all in the first week. Write as much as you can, but don’t post all at once. Here is why. When you start of you will not have any readers. If you spread your great posts out over time, you have a better chance of people actually seeing your content.
Obviously you can’t decide not to post anything until you have a bunch of readers, but unless your posts are time sensitive, don’t try to post 5 times a day when you have only 3 people subscribed. A better approach is to post once every two weeks for the first month or so, just to get your blog established and indexed in the search engines. Then start posting every week while you work on building subscribers.
Once you get some regular readers, maybe start posting twice each week and eventually move to once per day (if it is appropriate for your topic). During the time where you are posting once per week, you can still be writing content for the future. When 100 people read one of your posts, it has a better chance of spreading than when 25 people read it, so ramp up your post density as you acquire readers. Otherwise it is easy to get burned out.
The idea of posting slowly while still writing posts for the future also helps give you momentum. You may be only posting once per week with 10 readers now, but when you get to 50 readers, you have the ability to post twice a week without increasing the amount of time you spend writing because you have a pool of posts to pull from.
It use to be that simply having a blog was enough to get lots of readers because the amount of content (particularly blog content) was very limited. Now you have to get to a certain escape velocity before your blog really takes off on its own. By starting slow, you can reserve some of your momentum to push through difficulties. By difficulties, I mean the times where you may be discouraged because the number of readers you are attracting doesn’t seem to be growing or when you just don’t feel like writing.
Use a a slow start to build up enough good solid posts to help you slingshot and take advantage of opportunities. For example, lets say you are posting one post per week and suddenly one of your articles is featured on the front page of Digg. Immediately posting another killer post is a great way to encourage people to come back to see what you post tomorrow. If you have a pool of these posts to pull from, you will be ready to leverage a spike in traffic instead of scrambling to try to retain readers.