Now a days Blogging has become one of the major source of earning revenue.For this no qualifications are required,anybody can do this.the only required skills is basic computer knowledge,good english.
You can earn money in two types.
You can earn money DIRECTLY from your blog:In the “direct” option, you can show advertisements to your visitors or sell affiliate products[amazon,flipkart etc,,,] we can create free blogs in blogspot.com.
Earn money becouse of your blog:you can make money indirectly as blogging can help you find a new job or get freelancing work.
FOR DISPLAYING ADVERTISEMENTS ON YOUR BLOG:There are different advertisingprogrammes like google adsence,Chitika etc,,,,,google adsence
For Blogadvertising Blog Ads are the popular. They usually pay well and in addition to that they give you the freedom to decide that which ads are displayed on your blog. Another advantage is that BlogAds provide a fixed payment,they don”t consider the number of visitors to your site. However the draw back is that you just will gain entry into the BlogAds network, only your web site receives a good quantity of traffic and a few advertiser is willing to sponsor you. That might be a large demand for a new blog ,however established bloggers should think about BlogAds, provided they find sponsors
Google is the biggest and most popular advertising.Their Google Adsense programme is hugely widespread as a result of it offers discourse ads,which means Google spiders scan the content of the webpage on which Google Ads would be displayed then show ads supported the context of the content. Discourse Ads provide excellent returns, as web sitevisitors are more interested in about knowing about product that are associated with the content they’re reading.
Generally google adsence earnings can be two types
 cost per click [cpc],
Pay per Impression
you can able to check at any time that what are your earnings.Google which provide the ads based on your content.