So what type of ads do you have to put? That's the good part, you don't have to decide. Google does it for you. Adsense always delivers relevant ads that are precisely targeted, on a page by page basis to the content that people find on your site. For example, if you have a page that tells the story of your pet fish, Google will send you ads for that site that are for pet stories, fish food, fish bowls, aquariums … you get the picture else depends upon the often keywords you have used in your content, or you might target a keyword also. But everything is an automated process from google, it knows to which site they should target which relevant ads exactly.