A young kid who graduated from high school and after a couple of interviews, landed a salesperson at a big box store. Working in the air conditioner and heater department, a customer asked, "Can you please help me pick out a heater?" After some awkward questions (he didn't know much about the products), the customer bought from the young man. It turns out, he was a very effective sales person.
However, later, as he gained product knowledge, and wanted to impress the customers with his expertise, his sales fell off.
Learn to ask questions, "like a dummy", on purpose. It's disarming to the customer, and allows the customer to share their needs.