To add to Michele's response, which I totally agree with:
1. You can obtain fee schedules for various insurance companies either on their websites, or by requesting them directly from the insurance company. Some insurances also have a cost estimator on their websites. This will allow you to know exactly how much to charge the patient when they are in the office.
2. Make sure the doctor's contract with the insurance companies in question allows them to collect anything other than a copay upfront. Some do not.
3. If you are going to collect deductible money upfront, you had better make sure the claim is being submitted on the same day, or you will run into problems. My office does not collect deductibles upfront, and we submit our claims each day. More than once, we have met a deductible for a patient who already paid the deductible at another office, and that office didn't submit the claim until days, weeks, or even a month later. Thus causing the patient to be very irate with US when we sent them a bill for their deductible, even though they should be irate with the other office.