Families USA has put out a very good guide for people struggling with medical debts. The topic's bleak, but the advice can be critical.
In addition to the usual advice -- make sure the charges are correct, find out your appeal rights -- the 20-page booklet has good, real-world advice for folks who cannot afford to pay. It includes pointers on how to ask billing offices to write-off or forgive some of the bill, negotiate a lower rate, and what to ask for in a payment plan.
Other advice: Prioritize child support and income tax debts, since failure to pay can mean serious legal problems. Avoid adding medical debts to your mortgage, which puts your home at risk.
The guide looks at different types of bankruptcies, how to protect yourself if sued, whether money can be taken from your paycheck, and how to deal with bill collectors.