Earning money from blogging, is well, you need this article - http://www.techgau.org/2012/06/make-money-online-blogging-ultimate.html Im not spamming or anything, but this is a really good resource, mods can check it out.
There are lots of ways to earn blogging, the secret is find one way that works for you and focus on that. Good luck
Blogging is merely a tool to promote your core business. Whether that business be information, entertainment or something else. "Blogging" itself, just for the sake of blogging, will not make you any money no matter what anyone tells you. Unless you have a compelling reason for people to visit your blog consistently, you will only be able to achieve shortlived tricks...not any kind of sustainable income.
You can earn good money by posting other person blog in your blog by offering them some price money. And Adsense is the best way to get money without making and clients.
what besides hmansfield no one considered is the time it takes to write the blog posts, do develope the theme and to get the blog running by promoting it. It will take you way more time than you think first. Now let's say your blog is making a good 200 USD (which takes some effort to reach) a month I would assume you will have to work at least 30 to 40 hours within the month only for the blog. Calculating you will find you are not even making 10 USD an hour for each one you spend on developing your blog
If you have good content, it can be quite easy but requires patience . put in good stuff that people would want to look at (and not only what you like), make sure the theme and content of the blog coincide (a blog on Gothic literature with cheerful yellow-green template would be ridiculous) You need to get people to know about your blog. social media is big help. Decide how best you can get people to take a look at your blog (like a pic of Obama during elections might increase the value of your posts and status on fb, which can get people to view your blog). Once you are sure about the content and traffic, use Google Adsense. it is amazingly simple and useful. remember to keep updating and publicizing your blog. Guest blogging is another good option to increase traffic.