You know what CPA based advertising is, you need to know how it works. If you were an advertiser wishing to use CPA to promote your products or services, you would in the first instance approach an agency or awebsite that offers the facility of placing CPA ads. Once there, you will create your ad, possibly assisted by the agency or website, and as soon as you have done so, it will begin to display- almost immediately inmostcases.

Many of the leading advertising company websites will offer you several choices of advertising models that you can use on websites, blogs, and the search engine results pages that they control. These might include PPC, CPA, and also what is known as CPM advertising, whereyou will pay per 1000 exposures of your advert, irrespective of any actions that site visitors who see the ads might take.

However, assuming that you choose the CPA option, then it is most likely that your advert will be shown until a pre-specified number of the actions that you require have been recorded. For example, if you set up your campaign to generate 100 sales, then your adverts will stop showing once that targetis reached.

Again, as an advertiser, there arequite a few other things that you can use CPA advertising for as well. 

For example, you can:

• Use CPA advertsto test the effectiveness of your ads before launching a major campaign. After a CPA test run, you can quickly see how many sales have been generated by your campaign, and, although you will not necessarily know exactly how many times your adverth as been shown, you will never the less be able to establish how long thead has been running. From this, it will be fairly easy to calculate approximately how many sales you will be ableto generate from a more significant campaign if you were to use the same CPA strategy.

• Effectively allocate and spend a restricted advertising budget. The very nature of the CPA model means that this particular form of advertising is very effective in budge tary terms. If you're working on a limited budget, you will know from the out set that the only time you will pay for your adverts is when a site visitor takes the action that you specifically require of them.

• Boost sales performance. If you have been advertising using other methods, and enjoying little success, then CPA advertising represents an almost risk-free alternative that you might want to try in order to boost your sales figures.

• Use CPA advertising to test a new affiliate program. Sincemost affiliate programs are essentially CPA advertising campaigns 'dressed up' in a different guise, you can use CPA to test the effectiveness of any affiliate program that you plan to launch for your business without worrying aboutany longer term commitments to people who might choose to affiliate with you.

From a website or blog publisher’s point of view, CPA works in pretty much exactly the same way as AdSense or any other leading PPC arrangement. You would simply join an advertising website that offered a CPA option, choose the type of adverts that you want to show on your site, and finally copy a few lines of code from the site and paste them on to your web pages where you want the advertising to appear. You should then start seeing targeted advertising appear on your site almost immediately, and all you need do is drive as many visitors to your own web pages as possible, in the hope that they will see theads and click through on them.

Now, if you are using AdSense or another PPC advertising program, then this would be the point at which you would have generated a payment to be added to your account. Using CPA, however, the visitor that you have just sent to the advertiser’s website still has one more step to take before you can expect to get paid. 

This demon strates what is widely perceived as themain disadvantage of using CPA advertising. However, it should be noted that CPA programs will generally pay you a great deal more than you could ever hope to earn for one click using a PPC program, and this vastly increased payout per success does go quite some way to offsetting what many perceive to be the disadvantages of using CPA advertising. 

- See more at: http://blog.advertgoal.com/how-cpa-works