• The product has a good salesletter that makes you want to buy it.
• The product is priced reasonably and you can make at least 50% per sale.
• The main site is attractive and well thought out.  Not too many bells and whistles.
• The product goes along with the theme of your website.
• The company has good customer service.
•  You get recurring commissions with same customer.
•  No fee for signing up with company.
•  What is time frame of the cookie? (A cookie is a coded piece of information on a computer that identifies the computer when it visits the website.  You need a cookie that will be active for at least 30 days so anything bought in that time frame will be credited to you).

Make sure all these points are answered with a yes.  Nothing worse than signing up with a company and finding out they have major problems or a bad track record.  Do your homework first before you jump in.