the type of wood varies, but there is a tendency in some tougher breeds of vampire (lone antagonist-type) to only be weak against one type of wood. Iron is more commonly associated with the beings of the Faerie than with vampires. Salt is one we're not too familiar with a direct weakness to. The times we've seen salt used, it was as a spell component/carrier for witches or wizards rather than as a weapon onto itself. Silver occurs at times, but it too is more consistent with werewolves than with vampires, but its not as exclusive.