PLOT:
generally this is not a major factor. the people come to see shit blow up so you don't have to put too much thought into this part. The story can be extremely flimsy, as long as there is a reason for breaking into a warehouse full of ninjas at 3am, the audience won't care. Revenge is always a good plot device (Kung Fu: the legend continues, El Mariachi) or something in the interest of police work (Lethal weapon series, American Ninja), but there has to be a reason.
HERO:
Hero needs to be someone who has a real job, preferably blue collar, but for some reason is a martial arts master or an urban commando weapons expert. Mostly the hero is very ignorant of other cultures which can lead to some comedic encounters (Rush Hour, Enter the Dragon). Generally the hero is also extremely fast on the draw with wise cracks (The Last Boy scout, Die Hard series) and sometimes has a working knowledge of explosives (Die Hard 1, Rambo: First Blood)
VILLAIN:
villains are ALWAYS smart. mostly they are at least ten times smarter than the hero (Die Hard 1 and 3) but sometimes can be an equal for a more psychological thriller (Virtuosity, James Bond series). Villains are always bent on either world domination (James Bond villains), getting a lot of fast cash in a REALLY imaginative way (Die Hard 1 and 3, Goldfinger), or terroroizing the general population of New York or Los Angeles (The Seige)Villains usually push drugs and have lots of flunkies and assorted minions working for them, but even though the villain is always smart, the minions have the IQ of masking tape. In the 80's there was a period where almost every villain had an army of ninjas working for them but these ninjas were always marginally smarter than pond scum and always die horribly painful deaths. Flunkies are always extremely lousy shots. The average flunkie can train for several hours a day in the villain's specially buit training camp and pass the military equivalency weapons test, but the second the hero enters the room the flunky is unable to hit the broad side of a mountain with a tank shell from 12 feet away. Villains are allowed one sidekick who is smart but that sidekick is always second to last to die and it's usually someting pretty gruesome.
One other thing to note: VILLAINS ALWAYS LOSE. this harkens back to the old cowboy movies where the guy in the black hat always dies. If the villain escapes, you have a chance for a sequal, but you have to remember the ironclad rule of all action films: THE AUDIENCE ALWAYS SURVIVES. this means the huge lazer on the moon has to be disabled so that the people who just spent eight bucks to see the film can go home feeling like they narrowly escaped dying yet again, all thanks to (insert hero)
PARTNER:
Heroes generally don't have partners and have no need for one, (unless this is a buddy film like Leathal Weapon or Rush Hour. For this segment we will assume it is not) Partners generally serve as either a plot device (my partner was killed and i want revenge) or for comic relief. Generally partners die. either at the beginning of the film or at the end but it is usually a good motivator for the hero to do something bad-ass or get from one point to another (see PLOT) a great example is in Last Crusade where Sean Connery gets shot and Harrison Ford goes to get the grail and we watch Julian Glover age 6000 years in ten seconds.
WEAPONS:
The bigger and more noisy they are, the better. Heroes always know how to use them, no matter what they are or how exotic. Villains always have cooler weapons (Predator, Batman, James Bond) but the hero can always pull something cool out of his ass and defeat six guys with lazer guns using nothing but a spit ball and a coffee filter (Macguyver)
EXPLOSIONS/CAR CHASES:
if there is too much dialogue (more than six words at a time) throw one of these in. (Bad Boys) ONLY USE REALLY EXPENSIVE CARS AND ONLY BLOW UP MAJOR THINGS LIKE A FIREWORKS FACTORY FULL OF COKE
CHICKS:
the audience at an action film is predominantly male. Men like seeing tits. Hard bodied women help distract from having to think about the story, graphic sex scenes work best. Women can also be a good plot element (girl gets kidnapped and hero has to save her, girl betrays hero to villain, etc.) action flick girls are almost always foreign (Franka Potente in Borne Identity, Asia Argento in XXX, any Bond girl) and mostly have very few speaking lines. If the girl is not foreign (the exception being British) she can be REALLY smart (Elisabeth Shue in The Saint, Rene Russo in The Thomas Crown Affair (1999)) but invariably she will fall for the hero and want to (and frequenly does) have sex with him for no apparent reason, even though she despises him when they first meet and at the time of actual intercourse, the villains flunkies are shooting at the room where the fucking is taking place.