CPA stands for Cost Per Action which means that you get paid for generating leads. Compared with traditional affiliate marketing, CPA networks make it possible to get paid without making sale. This is a huge advantage and explains why many of the successful affiliate marketers have moved on to do CPA lead generation.
If you have tried affiliate marketing and want to move on, CPA marketing is a natural next step. If you are good at driving traffic you can make big money with CPA networks. Since you do not need a sale to make money, the conversion rates are much higher than in traditional affiliate marketing.
Most of the landing pages have a form that needs to be filled out in order for you to get paid. A lead can be as simple as just name and email address. But it can also be multiple pages, for example a mortgage application. Generally, the more information the visitor is required to enter, the more you get paid. Often the visitor does not need to pay anything, but in some cases a payment is necessary. Once again, you generally get paid more in latter case.
Becoming a CPA publisher or affiliate is a little bit more complicated than getting started in traditional affiliate marketing. There are a lot of CPA networks to choose from and you have to apply and get accepted by a network before you can start driving traffic and making money. Some networks are easy to join while others are more selective. You can join most networks even if you do not have a website. But they want to know that you can generate traffic for their advertisers. If you are using PPC, be prepared to specify your budget for PPC campaigns.
You should join more than one CPA network, two of the most popular are Hydra and Azoogle. Note that every network has its own terms and conditions. If you do not follow the guidelines, your account will get terminated. So make sure that you know the guidelines for each network and campaign. You can join most CPA networks even if you live outside the US.
You can also use CPA networks to get traffic to your own web sites. As a CPA advertiser or marketer you are taking a greater risk since you generally have to pay upfront. This also requires that you know how much a lead is worth to you.