Simply put it is irresponsible to go visiting without adequate insurance coverage. It isn't a risk for just you alone, but can also affect every one interested in doing pet visits. You don't have to be in the wrong to be sued. Lack of insurance is not just a problem for the person visiting, but can also cause the site problems. An incident is more likely to cause the complete elimination of visitation programs if it has adverse financial consequences to the facility.
Most organizations have a detailed evaluation process.
The evaluation starts with a temperament test and a health test. This is not, however, really good enough. If you are going to take advantage of group insurance you will need to be certified by the group carrying the insurance. The Delta Society, Therapy Dogs, Incorporated, and Therapy Dogs International are just some of the organizations that will evaluate and certify your dog. Provide proof of good health.