How are Ministers of Magic voted out by no-confidence?

Do all the Heads of Departments come together and vote? Or does the Wizengamot vote? Or is it a public vote? Or is it a vote by the Lords of Houses, as in Lord Potter, Lord Malfoy etc?

I know that last one is not canon, ie, in the actual books, but I mean each family sends forth their Head or a representative and they vote.