I see many questions being asked on serverfault that are more appropriate for superuser. I vote to move/close, and add a comment to so other regs will also vote to move. Frequently the original poster, will add a comment saying something along the lines of "I didn't know that site existed".
The ask a question page (https://serverfault.com/questions/ask, https://superuser.com/questions/ask, https://stackoverflow.com/questions/ask) do give you a somewhat useful idea of what is appropriate for whatever site the user is on in the column to the right.
The page does not give any good indications that the other trilogy sites exist and the focus of the other sites may be more a better location for them to ask their question.
I think updating the 'Ask Question' page to provide some better hints about the existence and focus of other trilogy sites is one way to help grow serverfault/superuser with on-topic questions.