I personally prefer to do it that way--you can create a more convincing review that's more likely to make sales. It's not always possible or practical, though; for example, would you break up with your significant other just to test a product for getting your ex back? ;-) In cases like that, or if the product is expensive, it's usually best just to use the vendor's affiliate resources instead.
One great way to get ideas for related products to promote is to look at the stats/reports that Amazon gives you to see which products readers are buying. After a while you’ll start to notice that they’re not only buying the products you directly promote but other products as well. Some will be completely irrelevant to your niche – but many times trends will emerge that could signal other products that it might be worth promoting.
Same thing as affiliate tracking. A unique ID attached to the links you use to send traffic to the merchant that is specifically for you to track your sales for or referrals to the merchant. Example of a tracking code in a link: merchant.com/?ID=YOURUNIQUEID – You'll find an in-depth article on what affiliate tracking codes are and how to use them here.
Now here’s the tricky bit: let’s say you’re part of the Amazon.com program (for the US) and you generate an affiliate link for Amazon.com. If I, a polite little Canadian, skates over to your site and decides to buy a giant jug of maple syrup from your link, you won’t get any commission if I end up buying from Amazon.ca. You will only earn commissions from Amazon.COM.
Affiliates were among the earliest adopters of pay per click advertising when the first pay-per-click search engines emerged during the end of the 1990s. Later in 2000 Google launched its pay per click service, Google AdWords, which is responsible for the widespread use and acceptance of pay per click as an advertising channel. An increasing number of merchants engaged in pay per click advertising, either directly or via a search marketing agency, and realized that this space was already occupied by their affiliates. Although this situation alone created advertising channel conflicts and debates between advertisers and affiliates, the largest issue concerned affiliates bidding on advertisers names, brands, and trademarks. Several advertisers began to adjust their affiliate program terms to prohibit their affiliates from bidding on those type of keywords. Some advertisers, however, did and still do embrace this behavior, going so far as to allow, or even encourage, affiliates to bid on any term, including the advertiser's trademarks.
There are two ways to approach affiliate marketing: You can offer an affiliate program to others or you can sign up to be another business's affiliate. As the business driving an affiliate program, you'll pay your affiliates a commission fee for every lead or sale they drive to your website. Your main goal should be to find affiliates who'll reach untapped markets. For example, a company with an e-zine may make a good affiliate because its subscribers are hungry for resources. So introducing your offer through a "trusted" company can grab the attention of prospects you might not have otherwise reached.