What services are you looking to purchase? If you're looking for a hosting provider, I wrote an article on this topic a while back: http://www.northrup.org/magazines/Managed/ If you're looking for Internet access, first consider the financial viability of the company--find a company that won't file Chapter 11 and leave you without connectivity. Next, weigh pricing, support, and the provider's upstream connectivity (how well the ISP is connected to the Internet). Good luck!
This was first published in December 2001