We have covered many aspects of paid search over course of this month however most of the points covered have been focused on the cost-per-click model and primarily in the form of Google AdWords.
The cost-per-click option is offered by many other search engines such as Bing while other search engines may syndicate the ads from the larger search engines to their search partners through a search network. Some of the other search engines known to syndicate ads from the larger providers include Ask.com (Google AdWords) and Yahoo! (Bing Adcenter).
Some of the smaller search engines and vertical directories offer alternatives to the cost per-click-model. The cost per impression (CPM) option is often used by these search offerings. This option guarantees your advertisement will be shown X number of times for your budget. While there is no guarantee that these ads will generate traffic for your business, these are good at building brand awareness through repeated displays.
Occasionally a directory or engine might offer an option to sponsor a particular page, section or search term for a period of time. This form of search marketing is usually found on what are known as vertical search engines or directories - those that deal with a single or a specific industry. While there is no guarantee on traffic generated from these ads, they are usually sold with exclusivity ensuring that your business is the only one that can advertise in your vertical.
Some advertisers offer a Cost Per Acquisition (CPA) option. This is more common among comparison search providers where many similar advertisers would want to promote their product or service alongside similar providers. This model is similar to the cost-per-click option (both being pay per action) however the advertiser only pays once an agreed goal has been met. This could be a concluded sale, a newsletter sign up or similar goal.
As with all forms of marketing, the objective of the campaign needs to be clearly defined before you start a campaign. Once you've got your objectives in place it becomes a lot easier to decide on which option would best suit your needs. Depending on whether you're looking to generate traffic, create brand awareness or make the hard sale there is a paid search solution for you.