From time to time, I find myself relying heavily on the advice of a vendor or shopkeeper when it comes to products or services I buy. It is because I am requiring expertise that I don't have or have ready access to. Electricians, painters and anything to do with motor vehicles are good examples.
If you or your staff are in a position to offer specialist service or advice, it is really important that when questions are answered that the answers themselves are complete and accurate. Anything and everything that a customer should know should be communicated. My modus operandi if asked a question to which I am not sure of the answer is to say "I don't know, I will find out and let you know" or to recommend someone else who will know the answer.
A really good example for me was in the simple act of purchasing a set of headphones for gym use, because the specific set required had to be excellent and particularly robust. The reasons being that a) the music in gyms is dire at best and b) it's no good having your headphones falling off "mid-set".
The ever-alert squad at Noel Leeming was well informed — they recommended and sold me the best set for the job. Unfortunately, I quickly lost the headphones so I expect to be returning shortly to purchase another set — not even the greatest salesperson can stop you from leaving a small appliance on the roof of your car.
I have also experienced the other side of this recently, where I have received representations about a product or service which have proved to be false or short of fact — and do you think I will be buying those products again? Uh, no.