Some years ago, I started a blog about Joomla, an Open Source Content Management System (CMS). I worked a lot on it for several years, and at the peak, I had around 50-60000 pageviews per month.
I started the blog because I loved to use Joomla. I still do, even if I don't blog as much these days. After a while, though, I needed the blog to generate some revenue. I couldn't defend spending that much time on a blog without getting some money in return.
The most obvious way to make money off of a blog is to put ads on it. I have done that - and the blog still features ads. The revenue from this is not amounting to very much - even if it covers at least some of the actual costs involved with running the blog (server, domain etc).
The other way of creating some revenue is to create a product. I spent a long time writing the book "Blogging with Joomla" and self-published it. It did OK, but I must admit I spent a lot more time on it than I was paid for. It still sells a few copies now and then, though.
One effect of creating a blog with such a high amount of visitors, is that you get in touch with a lot of people. The contacts I made through the blog have been invaluable for me as a web developer. Whenever I need a product, customization of some kind for a project, quick response support or whatever else, I know who to contact. Many times, I've received really rapid help, as well as free stuff, subscriptions and so on because of my role as a blogger in the Joomla community. I've also benn able to talk directly to the developers of various software to report bugs, get custom solutions built and more. This gives me a competetive advantage in my marketplace. My ability to serve customers increases because of my blogging.
Still, none of the above elements are what produce income from the blog today.
Revenue comes from unexpected sources
After blogging for a while I came in contact with a person that wanted me in on an online project as a partner. I joined up with him and the project has grown steadily since. It now gives me more revenue than I could dream of getting from ads, product sales or anything mentioned above. The income isn't related to the blog at all - the blog facilitated the contact and opened the door to a fruitful relationship.
The person in question trusted me from reading my blog over time. He believed in what I was writing and used my tips to improve his web sites. This, in turn, made him approach me for a collaboration. People do business with people they trust, simple as that.
Keep your eyes open
The point of my story is that blogging can lead to some pretty powerful contacts, leads and opportunities that you won't even imagine when you start out with that first post. Don't focus too much on trying to force your blog to make money. Make sure you build relationships with your audience. Simply put, build a network of people that trust you and that become your fans.
Opportunities will follow - make sure to catch them!