Anybody can start trying to make money online through Google Adsense. All you have to do is apply at www.adsense.com. They have a very strict code of conduct and should be taken seriously. You have the potential to make some decent money off adsense if your market it correctly.
Some tips I can give to increase your chances of success:
Develop good quality content. Also spending a little more time on a site can really pay off. From my experience making a ton of really badly developed content according to a popular niche isn't really the way to go. I like to develop something that may be useful to people for years to come, thus increasing your revenue for the long-haul. From the research and short experience ive had with Adsense. Developing good quality information is really the best way to go. Think of ideas by identifying questions you have about a particular subject and answer those questions in a blog. I believe a blog is the best way to start with adsense, you can get your feet wet while you continue to learn the game. Social networking can also be awesome for adsense. I dont mean spamming friend invites though Google really does have a very strict policy when it comes to spamming and plagiarism. But sharing your blogs with RL friends through social networking means.
Signing up for the major social networking sites is a must. Even if you only post your blog once that can become a very valuable backlink to your site.