The best way is to find a couple of people who're interested in getting hosting then offer them 1, 2 or even 3 months free hosting in exchange for feedback (testimonial). You can also ask the people who're already using the service what they think and their experiences with the company.
Ask the web host company to give you coupon codes or trials (maybe 1 month trial) for new members then promote that and ask everyone for feedback.
Hope that helps.