How not to plead a government liability claim under section 1983

Appellate Practice has this post describing an Eighth Circuit opinion affirming dismissal in a case under 42 U.S.C. 1983 where the plaintiff sued the government entity but failed to allege any facts from which it could be inferred that the constitutional violation was the result of the government's custom, policy, or practice, as required by the Supreme Court's ruling in the Monell case.

This sounds like the kind of argument that always occurs to me but I don't always have the nerve to make. It seems that my great ideas about ways to win motions to dismiss and demurrers are only about half as good as I think they are.