THERE ARE 22 KEY SALES DOCTOR PRINCIPLES. Here are a few of them ... To be a successful sales professional you do not have to be a born sales person. Professional selling can be learned and learned well. If you believe in what you are doing then you have every right to get really good at helping people to use the service or own the product you are selling. No-one likes being sold to, but everyone likes to buy. Don't just find out what your customers want, find out why they want it. Bob Day AO is a successful businessman, author and entrepreneur who is a Senator for South Australia.