It requires you have knowledge of the HIPAA law as well as FCRA (Fair Credit Reporting Act), and be ready to write some letters and take action. It can be a bit tough to do that research on your own, so a very nice person, named "WhyChat", decided to take it upon themselves and compile all of the information that is needed on a website at http://whychat.5u.com/hipltr.html - including the legal basis (violations can be pursued by the state attorney general's with annual per violation fines up to $1,500,000 - talk about motivation to comply with the law), step-by-step instructions, links to attorney's opinions and even sample letters for you to copy/use on your own. This process has a very high success rate. I've seen over 15 medical collections deleted from someone's report that way, scores increased over 110 points.
When you are dealing with medical collections, being familiar with HIPAA & FCRA is like going into battle with a bazooka when the collection agencies have a butter knife.