One method that is well documented in folklore, and also in travelers' accounts from the 1700s, is to separate the body from the head. And archaeologists have found several of these, for example a group of graves in Poland that were buried with their heads between their legs. On the other hand this was also sometimes done to criminals, either as a means of execution or after death, so not every headless corpse will be a suspected vampire.
As you might imagine from modern lore, some bodies had stakes or iron rods driven through their chests to hold them down. In older folklore this is always done to corpses lying in the grave; so far as I know its use on walking vampires is a modern notion.
This area of research may actually have been helped by sensationalizing news stories about these burials. It's certainly the only reason I know about them, and I suspect that Polish and Italian archaeologists might not even know that these techniques were used in both countries if the media had not spread these accounts so widely. I did a lot of research on this sort of thing in the 1990s and at that time there were very few examples in the accessible literature, none of them as clear-cut as these.