Actors who have some idea what they're doing, and perhaps a bit of talent doesn't hurt.
A script that is OVER two typed pages for a 2 hour movie, but somewhat less than 500 pages.
A plot not written by the Special Effects Department.
Dialogue that does not mandate some form of "the F word" one out of every seven words.
Camerawork done by a professional and not by the town drunk on a bad day with a handheld.
A director who has at least read the script an hour before they start shooting.
A musical score that doesn't sound either like they lifted it from a 1976 porn movie or that is trying to blast you out of the theater, or even worse, BOTH.
that's a start
In short. Go watch a "ScyFy" channel special, and take it as the absolute best example of what NOT to do.