Presenting to the customer who takes every opportunity to get your demonstration off track can be a big challenge for any salesperson so don’t feel alone on this. 

During your presentation when you mention the great grip on your screwdriver and the customer switches the conversation to the quarterback losing his grip on the football last Sunday what should you do? 

Initially, you will need to let the customer go on for a bit without interruption, and as soon as he stops for a second or two simply go back into your demonstration. Never ask a question about their topic, never give an opinion on the topic simply listen for a bit and move on. If the customer asks you a question about the topic they are on, answer it quickly and shortly, and while you are in control of the conversation go right back to your presentation. 

Since this customer may or may not be focusing and understanding what you are saying it is even more important than ever to trial close often and get an answer of understanding and agreement before you move on to the next point.