Affiliate programs are basically an arrangement with other websites to refer people to your site, in exchange for a commission on any sales those people make at your site. It can be a nightmare for your web designer or webmaster to determine which customers coming from which affiliates bought which products at which prices on your website. Then you have to keep track of which affiliates are owed how much, and pay them on time. Those are just a few of the troublesome areas of setting up an affiliate program.
On the other hand, successful affiliate programs can gain you a lot of visitors who buy.
The best example of affiliate programs is one that Amazon.com created. They help you to set up a link on your website to a specific book at Amazon.com so that people can buy a book you recommend. If the visitor to your site buys that book when he visits Amazon.com (by clicking on your link) you get a commission. It is easy to set up, you don't have to track it (Amazon.com does) and you get paid for making a recommendation you would have made anyway. Our Books page has some of these links on it, which makes this website an affiliate of Amazon.com.
Affiliate programs are places where you can sign up for large amounts of affiliate relationships at once, and where you can develop and manage hundreds of affiliate relationships, or just one. You can show banner ads or text listings or anything in between. If you've got a lot of these going, someone must be in charge of maintenance and upkeep. Broken links will need to be changed out. Links to sites that don't sell need to go, and you need to manage relationships with all those other websites and constantly monitor your inbox. This should not be scrimped if you want it to be profitable.
One of our clients swears by Rakuten Marketing. Another one likes Performics. We make no recommendations here. We used to recommend Commission Junction, but we've heard several complaints about their service. Commission Junction may still work for you, however, so check it out carefully with an eye toward whether you can afford it. If you have the advertising budget for it, these people can deliver a lot of traffic to your website.
For more such programs you can join to have other websites carry banner ads or other kinds of affiliate links that send people to your site, do a search at a plain English search engine such as Ask or Cortana or Siri or Google "How do I join an affiliate program?" and you will get plenty of instruction and advice on how to do this.
Most people studying up on affiliate programs are trying to become affiliates—to make money by sending visitors from their own website to another website. This can be an effective way for a website to make money when it isn't paying its own way through sales of its own products or services. Typically this would be a popular site that isn't selling anything, but provides some kind of entertainment or informational resource.
One of the best and easiest affiliate programs to sign up for is Google AdSense. Google will give you some code to put on your website that will work to show ads for other websites on your website, and you will get paid monthly for every click on those ads. If you have a lot of traffic but nothing to sell, this is a good way to "monetize" your website. Many popular bloggers do this.
If a website is getting tons of traffic but doesn't have anything to sell, affiliate programs can be a very good way for it to make money. If that is your situation—you have tons of traffic but don't sell anything—here is a site that lists tons of Affiliate Programs by category.
The flip side of that is a website that has great products to sell, but not enough visitors. Google also provides an easy solution for this problem, in the form of Google AdWords. That's where you'd sign up to be one of those websites advertising on other websites. This is a form of paid advertising; you will be bidding on how much you're willing to pay for someone to click your ad to be sent to your website. The specifics of how to do this well are beyond the scope of this page, but we do have experts in this area on our payroll, who have managed millions of dollars of advertising budgets for our clients. We know how to make every dollar spent on Google AdWords give you back the most sales, and we do a lot of consulting in this area. Feel free to call us for a consultation.
You can get a free affiliate marketing e-course with 120 videos on the subject from Affil-o-rama.
You need to carefully weigh the factors involved in keeping track of your affiliates, your customers and your commissions BEFORE charging into this arena and seeking out affiliates to send people to your site.
Also: be aware that most of the websites sending you traffic will not do it for 5% of the sale price of your item; affiliates will expect somewhere between 10% and 50% for each sale made by customers they send you. How much can you afford to pay as a commission for these sales? Your affiliates will drop your ad very quickly if they come to realize you are not paying them a lot of money—and paying it on time. Their ad space on their websites is very valuable and they expect to make good money from YOUR ad if they put it on their website. Which is all the more reason to wring every sale you can from your existing website.