Don't risk your name and reputation by associating with junk. Secondly, you will get questions from prospective customers. How you answer them depends on how well you know the product. And thirdly, if you really want to sell the product, and lots of it, you must LOVE the product. Because it is your enthusiasm that will sell it.
Nothing sells better than a personal recommendation.
If you have joined an affiliate program, you have probably wondered about ways to promote it. If you have ever posted ads, submitted to search engines, done the FFA things, you have no doubt noticed that other affiliates in the same program were there before you. One thing you could do is look for a marketing or related site that gets a lot of traffic. Now, when this webmaster promotes the program on his site, it is seen by large numbers of targeted prospects. Then you move on and approach the next webmaster.