Tonight I happened to be vegging out in front of the TV (sorry... call planning for tomorrow) with a glass of Valpolicella Repasso. The programme was a thing called Antiques Roadshow, which I'm sure most Brits will be familiar with. The debonair presenter was holding forth about the exquisite nature of the Georgian snuffbox that he was holding before the camera. Unfortunately my attention wasn't on the antique, but was drawn to the poor guy's thumb nail which looked like it had been beaten repeatedly with a mallet for about five hours. I think the cameraman may also have noticed because he kept trying to pan across so that the thumb was out of shot, but the presenter kept waving the snuffbox to and fro and bringing the offending digit back into focus.
One of the more prosaic sales tips that I've come across during the many trainings I've attended is that of not using your finger to point when presenting to the customer. In a similar fashion to my Antiques Roadshow friend, you do not want to distract the customer's attention from the document/sample under discussion... so use a nice clean pen to indicate. This advice may, of course, be a bit dated nowadays when you could well be using a projector to present, however if you are one-to-one and showing something on your laptop, it still applies.