Know your Medicare modifiers for covered and non-covered services and be aware of the LCD diagnoses. Know the difference between a supplemental insurance and a true secondary insurance. And if the doctor is not a participating provider, he/she needs to understand that if you bill Medicare or even give the patient a super statement to get reimbursement from Medicare, they (Medicare) can review your records any time they want.
We keep running into doctors who think if they don't bill insurance, they can make up their own rules. Not so.