I'd assume that the best practice would be to use a code versioning tool, one that forces you to check out a document to make updates, then check it back in before anyone else can check it out. Our shop plays more fast and loose because we rarely have more than one person working on a document at the same time, and when we do, we're just extra careful and communicate verbally. "Be careful" is hardly a best practice, though. I thought I heard rumor that QlikTech had recently bought a code versioning tool and might be expected to include it with future versions. If so, it was in some thread somewhere, but I don't remember which. I could be repeating blatant falsehoods for all I know.