If you write blogs the key is content and getting people to visit. Clicking “ads” only pays off if your keywords are high enough. If you have a rare keyword, you’re only going to get pennies per click, if that.
In Google’s Adsense for example, the second bidder sets the price.
For instance, if I write a blog about Coyotes and the first bid is $10.00 for the word Coyote and the second bid is 3¢, then Google gets paid 4¢ per click. What percentage of those 4¢ clicks Google pays you varies. Not all ad schemes work like this, but Google does.
Let’s say you write a blog about Road Runners and that is a “hot” word. So the first bid is $100 per click and the second bid is made by an advertiser willing to pay $95 per click. Then the click rate is something like $96.00 per click.
Again it’s always the second person’s bid that sets Google’s rate
This is the key to making money through Adsense. You have to find words that pay well. Note for Google a “word” can be a phrase as well.
Computer type blogs tend to pay the best, as the get visited the most and they are visited by a ton of people looking for solutions to their computer issues.
As your blog becomes popular you can lose the format and go to a regular type website and start negotiating with your own advertisers direct for better rates.
The best blogs tend to be promoted very quitetly. For instance, if you say, “See my blog for the best computer advice” people tend not to care or look.
If you go to boards like this one and just offer advice without mentioning your website people will come to you. They will trust you as well.
The key is content, keeping it fresh and keeping it updated. No point in offering helping computer advice if you don’t take down the old outdated help bits. It just frustrates people.
Online advertising is not a very successful way to go. Amazon and eBay the biggest two have a click through rate of about 29% and 19% respectively (Source: SearchEngineWatch.Com). That is for every ad they run about 29% or 19% actually CLICK THROUGH to the ad. This DOESN’T MEAN BUY, but means mearly click on the ad. Their sell through rates are even lower.
I know of one person who has his own website and after years finally got some paid ad sponsors and does about minimum wage (8 hours a day) with it. And he WORKS hard at it. He is constantly updating and going to various radio/TV boards to help people out and he is a young guy who writes simply, effectively and respectfully.
But for him it’s a “passion” and to make less than $50 bucks a day, while he goes to college is OK, but it’s probably easier to get a job at Starbucks. 
