My confession: I have frequently tipped servers in restaurants/bars I've worked at to pick up signed cards I've palmed off and dropped on the floor behind me and to go outside and stick them on the window with a little piece of double stick tape. After having the spectator look through the deck to find their card has vanished, their attention is, of course, directed to the window, where they see their signed card staring them in the face. This has cost me some money, but I think I have made a profit considering the tips the trick has gotten - not to mention the priceless reactions of the patrons and the good will it builds with the servers.