People begin venturing into making money with Google AdSense by creating a website or a blog based around anything that they can think of, usually what happens is your website will receive visitors but you will get very little if any type of visitors that click on your AdSense ads...
How come? Well first you have to understand the reason why someone is thinking of even considering clicking on an ad in the first place.
They are looking for more information pertaining to what it is they are searching for, if you provide everything they need on your website they will have no need to go anywhere else for that information.
Remember that the end user doesn't care if it costs an advertiser money once they click on an advert, they are only concerned in finding out what it is they are looking for.
Actually, the majority of everyday Internet searchers have no idea what AdSense or AdWords is so that is a benefit for you because if they did know people were being charged they most likely would avoid clicking on those type of ads.
Supply enough information to spark their curiosity but leave enough room for them to want to look for more information, the moment they see an ad that is relevant they will be urged to click on it to continue their investigation.
Don't create websites based around generic subjects that really don't involve any more need to keep researching on.
Create websites based around reviews or products as these are some of the best type of AdSense websites that you can create, people looking for this type of information usually are more inclined to keep clicking once they see more ads because they either want to know more about that product or look more in depth for more reviews before they decide to make a purchase online.