However, for me, the definition of the art or science (depending on your viewpoint) of selling is very simple: "Selling is the act of helping people to buy without regret".
We have all heard horror stories about pressure sales tactics and misleading sales literature and conversations being used to close sales, but that really isn't selling. It is just lying to achieve a temporary objective. It reflects badly on the salesperson, the company and the brand. In these days of social media the individual buyer as well as the business buyer are empowered to cry 'foul' and seriously damage anyone involved in unethical sales practice.
It is therefore, much simpler to just treat potential buyers as you would wish to be treated. Be a person first and a salesperson second. Ask questions and listen to the answers. Define and fully understand the customers wants and needs. If you have a solution to their problem, present it to them in a clear and concise manner. Let them ask questions so they can fully grasp what you are proposing. Be honest and transparent. Agree next steps.
It's not hard to be a good salesperson.... just be a good, normal person.