An interesting question, because many people now start blogging to earn some additional income, inspired by some top-bloggers earning remarkable amounts by just blogging. But is it indeed realistic to expect a blog to become a considerable income source? Most of the time it's not. Why?
Why do you have a blog? Is it because you are seriously interested in sharing your opinion on some special topic ( like programming and usability here ) or just because you think that everyone should have a blog, just like a linkedin or facebook account. There is no need to have a blog, seriously, and if you have nothing to share, don't force yourself to. Commenting on someone else's posts can be very satisfying, too.
And even if you really do have something to share, be prepared to be just one of many. It's hard to really distinct yourself from the tons of bloggers out there. You can do so, of course, by choosing a different language, a different style, a yet uncovered topic ( though I guess that's hard to find ) or some other factor I didn't think of. If you do so, because you just feel like, chances you will be successful in monetizing your blog aren't bad. Most of the time, however, blog posts are mostly generic in terms of style and content.
So now we're passed that point: Be very unique. That's certainly a way to attract visitors, and most of all keeping them. But even if you do generate a certain amount of traffic each month, you still don't earn money. Once again: interested users will find your blog, and if not, the blog is not interesting for them. Simple truth.
Now, assuming you've got your few thousand impressions each month, you really need to monetize it. And it's been a long road already. Start thinking about Google's AdSense, though it doesn't seem to generate amounts bloggers sometimes think they might get. Be prepared to earn just some dollars, nothing spectacular. Remember, people still need to click on a link actually.
There are other ways of selling your blogging soul. One is to do paid product reviews. Another is the old-school banner. Decide for yourself what you are willing to give up. Because visitors will notice change, and advertising or the attempt to monetize your writings may offend them. Think about that too.
Or just be happy without all the money-hassle and, assuming you are working like 5 hours a week on your blog, it's pretty fantastic to believe that 5 hours a week can generate enough money to make it worth mentioning. And even if you want to earn money, keep in mind that even one of German's top bloggers, Robert Basic, gets an income from about 3000€ each month. And he certainly has traffic...