The ultimate aim of every website is to earn money so adsense is now the most common and best option. you can add adsense in your wordpress blog in number of ways. Bu manually or by installing some plugin.
This the below list of vidoe sites posts to learn more…
Insert Adsense Ads with WordPress Plugin Adsense Widget
Setting up AdSense on a WordPress Site
Google Adsense for WordPress Sidebar (Widget/Plugin)