identify the purchaser if an purchase order is used , if in any doubt verify with you customer before taking the order that the client or customer in authorized to purchase for their company.
collect the shipping address on each and every charge invoice, signatures should be legible, scrawl is unacceptable and must be accompanied getting the habit of printing.
if you are taking down all the important information from the professional individual that will require you to get back or intouch to them, always make sure you repeat back to them what you have written and secure their agreement that you have information correctly.