A hosting company's support services often goes untested, especially with beginners in the site design and hosting world. A skilled and prompt support staff should be one of the most important decision breakers in your mind. If you run into trouble getting a perl script to work, or perhaps your database permissions are not setup correctly on the hosting company's side. You want those problems corrected, and fast. One way to test a service's support staff is to simply send them an e-mail and see how long it takes for a response to be sent. Try to send an inquiry to support and sales and any other department you deem necessary. Ask support if they offer a web language that you like, or ask the sales department if they charge your credit card or hire another company to do it for them. If you receive a response the same day, you can probably rest assured you will receive timely help with any inquiries you have. They should not take more than one complete day to get back to you.
Perform research away from the company's web site. Ask questions through e-mail lists and other mediums to try and get some feedback. If the company lists a testimonials section, look into contacting the authors of the testimonials and start asking questions. The more comments you have, the better understanding you'll have on how that hosting service treats its customers.
Pay attention to how long they have been online. A well-established hosting company of many years will most likely yield the greatest chances of customer successes. Click on the about page if they have one and read it all; after all, you may very well be giving this company your credit card number.