Medical liens

What's the process for getting a medical lien? Is the person being sued guaranteed to be notified? What if he is NOT notified and goes to sell his home later--how do you reverse a bogus default judgement?
I say bogus because my understanding is that to "notify" they're supposed to send you a letter--but they don't have to do certified return receipt requested or anything so they can easily simply LIE and then YOU are screwed. No PROOF that it was sent or to the right address or anything appears to be required from horror stories I have heard.