To many Ads ruin a site and its diffulcult to get people to click them i would recommend conduit - you make your own toolbar then put a few ads on your site to advertisie it and when someone downloads it you get money. Alternativly you could download it your self and get paid . www.igames.x10hosting.com -my site with an example at the top of what i meen
It seems everyone else support the ad thing. But one thing
you should know is that, not all sites can earn you money through ads
If you choose to use ads, then it should be adsense.
:You can likewise try better affiliate programs or cpm if your site is going to receive serious buyers
Google Adsense is probably the best place to start.
Then you need to have a good hard think about the content of your website, for the adverts to work people have to want to take a look at your site in the first place. Without this you will be lucky to earn a single penny no matter how many ads on the page.