A lot of people have a full-time job making money online. But there is an equal amount of people who see making money online as more of a recreational bonus. So if you have some spare time, have a hobby you love, and like the internet, then you could see some extra cash in your account every month.
The first thing to do is to identify some good keywords for your particular hobby. There are many free guides on the internet which teach you how to do keyword research. Essentially all you have to do is build a list of good keywords (the words or phrases that people type into search engines when looking for a particular topic) and then you're ready to build your blog.
The second thing to do is to build you blog based on your keywords. Again, there are a wealth of resources available to show you how to properly construct your blog on a foundation of keywords; If you do intend to make good money from your blog, I would strongly suggest doing some research on this or to invest a small sum into an ebook which teaches you how to do it step-by-step. You can build a blog at Blogspot or WordPress.
Once you have your blog formatted, you will come to the fun part – posting! Start writing about whatever you like, upload pictures and articles, and make your blog a passionate reflection on the strength of feeling you have for your hobby.
The penultimate step is to monetize your blog. There are two main ways to do this. The first is to browse sites such as Clickbank or Commission Junction and to find products which are related to your hobby's niche. The sale of a product you link from your site will earn you a set amount of commission. The second way is to install Google AdSense on your website. This is a form of text advertising where the adverts printed on your site are determined by the common words used on your blog. It's quite magical, and you will receive money every time a visitor clicks on one of those adverts.
The final step is to drive visitors to your blog. The more visitors you have to your blog, the more money you will make. Your best bet is to start off by joining lots of forums and newsgroups related to your hobby's niche. Simply add a link to your website in each of your forum profiles, and then start posting regularly to the forums. Alternately, you can write articles based on your hobby and submit them to free article directories like EzineArticles.
This is a very brief overview. Each step is an art in itself and you should realize that building a blog is an internet hobby that makes money. It can be a long process but, absolutely, one you should enjoy. It is always a pleasure to build your blog a little, day after day, and to see more and more visitors arrive. It's quite possible you can build a big presence online and become something of a guru, but most importantly you will have extra cash rolling in.