You know the em-dash—it’s what divides the two parts of this sentence. According to Garner’s Modern English Usage (GMEU), “The em-dash is perhaps the most underused punctuation mark in American writing.” But in my experience, once people start using the em-dash, they quickly start using it promiscuously.
That’s the case with me, with one exception: I don’t use it in contracts.
GMEU says that “A pair of em-dashes can be used to enclose a parenthetical remark or to mark the ending and the resumption of a statement by an interlocutor.” But it’s best not to use parenthetical remarks in contracts, just as contracts isn’t the place for nonrestrictive clauses (see MSCD 12.52).
GMEU also says that the em-dash can be used to replace the colon, but I don’t see the point of alternating between colons and em-dashes. In contract drafting, consistency is a virtue—stick with colons.