Since most bike shops rent bicycles, it isn't surprising that I get asked a lot of questions pertaining to the importance of waivers. Often, I get asked about the need for waivers, where to get a waiver and whether the insurance carrier can provide them with a sample waiver. First of all, bicycle retailers who rent bikes absolutely need a waiver. They need a waiver that has been drafted by someone admitted in the state where the shop is located. Interestingly, many waivers are "null and void," unless they have specific verbiage in them. For this reason, the insurance carriers want to have a local attorney, who knows the specific-state laws, draft these. Some waivers are better than others, and, in some states, waivers hold up much better than other states.
For more information on how a well-designed rental agreement/waiver can hold up in court, read this article by Alexander "Sandie" Pendleton: Wrongful Death Claim Against Business That Rented Snowmobile Barred by Waiver Agreement. Though it's a snowmobile in this care, it could just have easily been a bicycle.