HOw will I know if Im earning with my blog. I have lots of readers in my article.. and how would i know?

To know more about your blog earning and also how many accessed what particular information in your blog, what they are keen to know about in there. Also, which particular section really impresses them, to know all of it, best way is make an accountt on "Google Alerts", which is free of cost.
Google Alert over there you can see put an alert after every week, hour, day basis and over there you will come to know all about your blog.
Also if you create your account on "Google Webmaster" then again you will come to know how people are getting attracted towards your blog.
Since Yahoo! aswell uses Google as its default Search Engine Provider, so it will help you in getting exact information from there as well.