Regarding policies and procedures, we include all of the fine points and responsibilities that are both ours (the billing/practice management company), and the providers in our contract. We specifically outline what information is needed from the provider, when, how it will be transmitted, etc. We also include what we will do and in what time frames, fees, charges, etc, who is responsible for what, who is not responsible, and so on. I have revised this document many times over the years and have included things as they became issues such as invalid information from patients, refiling of claims at no charge in such an instance, nonpayment of our invoices by the provider/client, legal fees when pursuing collecting from clients, collections, A/R, reports provided, coding education, enrollments, etc.
I used a 'canned' contract many years ago, and this may be a good starting suggestion for you. As I mentioned, I have revised ours many times over. I thought it best to have everything straightforward and in a legal document from the start of the relationship. (And also including in that contract that it may be addended as necessary!)