Google placement advertising is a great advertising instrument to use. When developing an ad campaign using Google placement you can search for your target market in these four ways. Remember you have the option to do CPC (cost per click) or CPM (cost per impression) when setting up a placement targeted campaign.
i)    Browse Categories; where you can pick from a large list of categories and sub categories to choose the specific target you are seeking. You then can view and choose from a list of websites in which you want to place your advertisement.
ii)    Describe Topics; here you can type in topics. Google then searches for websites that match the topic you listed in the search box.  You can then do the same thing and view the websites and place your ad where you would like.
iii)    List URL’s; you actually type in URL’s to see if they are available under the Google AdWords system.  Let’s say you were browsing around one day and you stumbled across a website that would be perfect for one of your ads.  You can then use this tool to find out if you can add this website to one of your ad groups in order to place one of your ads on the website.
iv)    Select Demographics; finally you can search for a specific demographic that is the buyer for your product or service.  You can search by gender, age, and income.  Once you have picked the specifics you are after a broad range of websites meeting that demographic will appear from you to choose from.  Again you choose multiple websites and have now specifically targeted your ad campaign.