And now here is my addition to that.
Never criticize a prospect/buyer's previous buying decision. Never.
Why? Because you are telling them that they make bad buying decisions, and that they shouldn't buy from a salesperson.
Even if they didn't buy from a competitor, don't degrade your competition. Because if you do, you are talking down your entire industry.
So...what if they bought something that made no sense? Compliment the decision. Why? Because you want to affirm to them that buying is good. Buying is the right thing to do. Buying will get them compliments.
I know that this sounds manipulative and simplistic. But I can tell you from decades of sales experience...and decades of watching incompetent salespeople destroy any chance of a sale...this is often the cause, insulting a previous buying decision...or insulting a competitor that the sales prospect has considered.
And...you never know the story of their previous decisions. What if it was recommended by their brother, a beloved Aunt? Now you are criticizing a loved one without knowing it.
So...what do you do if they bought a bad product or service? Compliment the process they went through to decide. Compliment the fact that they took action. Compliment the fact that ...at the time...they decided based on the best information available. Compliment the fact that they did something to help themselves (or their family/business) And compliment the person that recommended this previous decision....because they had the customer's best interests at heart. And they were going with the information available to them at the time.
And now they have new information...new options available...they can make another good buying decision.
The important thing here is that the prospect is able to Save Face. Insulting their buying choices lowers their feeling of Self Worth. And if you insult a previous buying decision...the only way the prospect can get back their feeling of self worth..is to not buy from you.
And you'll never know what happened.
My 2 cents.