Now the advice I should say is "ask your lawyer"!!
Generally, if you have insurance with good policy limits and assets that are not protected by a bankruptcy filing, then you would be a candidate for a plaintiff's attorney to bring suit against. If that is the case, get a lawyer licensed in your state to draft one for your specific needs.
Most of these liability waivers are crap though, especially the free internet ones. A person needs to know that they are construed against the draftor, meaning if you found it on the internet and provided it to someone for signature you would be the draftor. Any holes or mistakes in it will be taken in favor of the other party. A good attorney can get around most waivers. What they can't easily get around are statutes and case law - that is where the creative arguments and case building begin.
Insurance agents are big into getting their insureds to use waivers. Well guess what - in some cases the insurance company will try to use your waiver to say that they have no liability to pay a claim. If an insurance agent wants you to do a waiver - ask them to provide it and then send them a letter stating something like "per your direction, I am having my clients sign the waiver provided to me by your company"
NOTE** This is not the case for contractual issues like horse sales or boarding - people, get that stuff in writing. ANY writing just do something.