If you're talking to an expert, show your expertise by sounding as if you've spent your whole life in his industry. If you're talking to a neophyte, don't embarrass him with your technical jargon. This is especially true in retail sales in which customers look to salespeople for guidance, not confusion.
Every field has its own jargon, and you may be an expert in yours; however, your prospect may not be as well versed as you. Avoid questions that will confuse your prospect or worse, make him feel inferior.
Example question not to ask: “Was the baud rate of your present system satisfactory?”
Example question to ask: “Were your telephone transmissions of data fast enough?”