I've got into the practice of creating two copies of a receipt of sale and collection, with photographs of the item and serial numbers, and asking the buyer to sign for collection and I sign for sale. I tell them straight that it protects both of us, and gives them something to show the insurance in the event of the item being stolen.
Everyone has been very happy to sign, though one chap I didn't entirely trust and I discretely photographed his car on my drive as well. (Not this item btw)