Wouldn't it be nice if we could post our little hearts out, sit back, and watch the dollars roll in? The truth is that there are very few people getting wealthy from blogging. If you're doing it solely for the bucks, you're probably going to be disappointed.
There are, however, a few ways to generate a bit of bloggy income.
The most obvious way to earn income is by having ads in your sidebar, or elsewhere on your page. You can try selling these yourself--a lot of work, but it works for some people. Many bloggers have had success using an ad service that sells the ads for you, giving you a percentage of the income. (They give you the code to insert on your blog, and your ads will appear in that spot. Any ad service worth its salt will offer you pleny of editorial freedom to block certain types of ads from your blog.) BlogHer Ad Network is an example of an ad service. At the writing of this post, they are currently accepting applications for new bloggers.
BlogAds is another favorite of many bloggers. You have to be invited by an existing BlogAds member to participate (though not every BlogAds member is authorized to give out invitations). BlogAds is attractive because it can be highly specialized. A company can buy an ad on JUST YOUR BLOG, not on every member of the network. Also, in BlogAds, you can group your blog into "hives" with other blogs--for example, Christian Blogs, Tech Blogs, Southern Blogs, Pet Blogs, etc.
PayPerPost has been popping up around the blogosphere lately. I'll confess to not knowing much about it--I've been a little turned off at the notion of being paid to "plug" a product or site actually in the content of my blog. A sidebar ad is clearly an ad, but a post? That's walking into some murky waters with your readers, who want to be able to trust you!
GoogleAds is yet another ad service some bloggers are having success with. It works by "reading" what kind of subject matter you're writing about and then posting links on a similar subject.
Amazon Associates is a tool I'd highly recommend to anyone who blogs about books. Once you set up an account with them, they help you build links back to their specific products. If anyone visits Amazon through one these links, you receive a referral fee from anything they bought in that session. It's very easy to do--their web site will walk you right through it.
As you would expect, earning ad revenue is based entirely on blog traffic. The more traffic you have, the more you can earn. If you're a blogger with low traffic, but you'd like to generate some income, my best advice would be to focus first on building up your traffic before going after ads. Write well, and consistenly. Consider your audience. Join webrings. Once you're feeling more established in your traffic, then you will likely find adding in these ad features much easier.