Advertising networks aren’t free – at least worthwhile ones aren’t. However, the best networks will bring enough converting customers to your site to make them, at the very least, cost-neutral; at best, highly profitable. And there’s always the option to join an ad network as a publisher, where you can make between 50-80% of the advertising revenue by displaying ads on your website.
Google Adsense (where ads are displayed on partner websites) and Google Adwords (ads appear on the Google search results page) are the widest used advertising networks and suitable for businesses of all sizes. You can choose from text or display adverts and the ads served attempt to be relevant to the hosting website content or search results. There are options for remarketing and demographic targeting too. Sign up with your Google account for free. Google Ad Exchange is their real-time marketplace for advertising trading and has an 80% publisher share. Prices of ads on Google depend on the popularity of keywords or the hosting website.
OpenX is possibly the next largest advertising global network with real time ad exchange. Media.net is the contextual ad network run by Bing and Yahoo which allows you to modify ads to reflect your site style too. Other advertising networks worth checking out include Sonobi, Conversant and Adroll.
Advertising on individual websites
Facebook offers relatively low cost per click (CPC) rates along with good targeting options which mean your ads get served to very specific groups. You can sponsor Twitter posts too and their platform has good targeting and reporting. The price you pay depends on the specific goal targets you define, such as more followers or retweets.