A fashion designer said the worst fashion mistake he sees all the time is "a bad haircut". Said people should spend as much as they can to have their hair look good.
So my thought on the worst fashion mistake an association exec can make is a bad handshake. I honestly cannot stand it and remember that detail about someone. Unless there is truly a medical reason for it (and there can be), how in the world can someone not learn to give a firm handshake?