When it's advertised as... "The Best Family Movie of 2016" and it's only February
When the poster have comments like: "Better than The Godfather", "Scarier than Psycho"
Forced romance plot in a non-romantic movie. (Edge of Tomorrow)
When all the media hype ends on the day of release.
Not screening for critics is really the surest sign.
Crotch injury in the trailer.
Really quick cuts for the trailer
A sequel announced with a lot of the original cast missing