You need some Characters:
There is a bad guy and a good guy. The good guy isn’t perfect, but he’s not as bad as the bad guy, who actually has some good qualities and may articulate his point of view very clearly just before killing his victim.
Everything that can go wrong for the good guy does go wrong. His situation is hopeless…and he’s angry. If the good guy is a cop he never ever calls for backup. The good guy has a wife, girl friend and/or kid that the bad guy will take hostage later on.
If the good guy’s a cop he can be a recovering alcoholic, but maybe he’s not recovering. In any case, his wife and/or girl friend can’t deal with him, and his bosses, while they may secretly admire his results, do not like the way he gets them. He’s very probably a loose cannon. At least one associate cop can’t stand him and they’re in constant conflict. We see that the associate cop would love to get something on the good guy. As mentioned above, The good guy has a kid just waiting to be taken hostage by a bad guy.
Somewhere an expendable (read ‘asset’ if the good guy is connected to the CIA), has to be facing the camera in close up while waiting to be struck down from behind by an assailant he/she didn’t see coming, preferably when he just learns something that may help the good guy.
The good guy has an acquaintance. He’s a whacko computer nerd who can hack any computer in the world, or alternatively he’s a whacko weapons freak who has in his closet enough weaponry to start WWIII. The key word here is that he’s a Whacko.
The real surprise bad guy turns out to be the good guy’s closest friend/mentor/boss/associate, someone who is completely above suspicion until the end.
In the end, the real bad guy gets the good guy cold and his finger is tightening on the trigger (cut to trigger) and we hear the shot, but then the camera pulls back and see that the cop who never liked the good guy has come up behind the real bad guy and nails him just in the nick of time.
You need Locations:
There has to be an abandoned factory for a hair-raising cat-and-mouse game between bad guy(s) and good guy. If you have a Terminator budget you can use an operating factory, but for everyone else, abandoned factory is the way to go. This is also where the gang always meets, where they take people to beat and/or kill them, brutalize women, and where the good guy inevitably ends up, alone of course.
There absolutely has to be at least one scene on, around and/or under one of the downtown LA bridges and/or in the usually dry riverbed below. Maybe there’s something in the Los Angeles City Charter making this mandatory. This holds good even for big budget movies like the Terminator franchise, so it cannot be overlooked.
And The Conclusion:
In a bittersweet ending the good guy and his hostage are reunited. All is forgiven and he has been vindicated and justice has been served. We however, have not been served; we have been taken. (Again.)