facebook ads
bing ads
That's a very vague question...
Generally you want to provide a solution where people are actively seeking one, one of the best ad placements I recently was a bus bench ad placed across the street from the back entrance of a police department, it's the last phone number someone who has been arrested would see.
Sponsored search ads, like Google's Adwords can present your message to people with buying on their mind, when the right search keywords are selected. Adwords is expensive, it's an easy way to lose lots of money if you don't have an optimized sales page, ideally one would have a landing page with a known average visitor value before committing to expensive advertising traffic.
Google/Bing and Facebook. Why? You can target your audience and reach to niche market. If you develop your campaign intelligently you can make profits too:)
facebook page,twitter is best place to advertise your add.the more likes you get,the more popular page you will be,and your add became popular.its amazing.i lovin it.
That depends on your target market
