The Scream series was famous for enumerating the rules of the slasher horror genre. The Creature Feature has its own rules, and the best movies play by them -- or play off of them. Here's my take on the rules of the genre; feel free to to add your own in the comments.
Rule #1: Don't show the monster
As I mentioned in the Jaws review, one of the things that makes the movie so effective, and what makes the tension so intense, is that you don't see the shark for two-thirds of the movie. You see it's wake, you see the surface attacks, but it's not until the third act that we really see the monster.
The most successful creature features follow this now predictable, but still effective, approach but there are variants. Alien and its progeny are the best examples of this. The film hides its namesake creature until halfway through the film, but it provides an equally effective horror in the form of the face-huggers. These insectile parasites are hatched from eggs, and latch on to anyone who gets to close to them. That's creepy enough, but then they implant the alien embryo which incubates in the body for a few hours. It then bursts from the chest of its victim and quickly evolves into the full-sized monstrosity we've come to know and fear.
Rule #2: Listen to the scientist
Every creature feature needs a scientist -- or the equivalent there of -- to explain the creature and come up with theories on how to fight it.
In Jaws, it's shark expert Matt Hooper. He works brilliantly, describing the beast that we can't see, providing well done touches of humor, and giving us a geeky protagonist.
InAlien, it's stoic, murderous Ash, the company scientist who analyizes the Alien's parasytic life cycle and suggests fire as a means of combatting the creature. In the sequel, it's the android Bishop who takes over that role, and theorizes about the existance of an Alien Queen.
In Tremors, it's cute geologist Rhonda LeBeck who's in the valley researching earthquakes and theorizes about the creature's weakenesses. In The Thing, it's Dr. Blair. It's not mandatory --- Predator lacks such a scientist -- but the infodumping scientist is a fixture that serves an important role in justifying the existance of such a horror.
Corollary: Once the scientist has served his purpose, kill him.
Rules #3: Give us protagonist we care about
It's not all about the monster: you need people to care about or the rampage ends up being little more than blood and gore. Jaws gives us three: down-to-earth Sheriff Brody, nerdy scientist Matt Hooper and grim (and more than a little crazy) shark-hunter Quint. Alien and Aliens gave us Ripley, first as a young officer, then as a pissed-off mom. In both cases, she was someone you wanted to root for.
In Deep Rising, we've got Finnegan and his crew. Sure, they're a ragtag band with an equally erratic ship, but they're the ones you want to cheer on when they're using a jet ski to flee a horde of hunting tentacles.
Corollary: If you can't give us a protagonist to root for, then give us one to hate. And then kill her in spectacular fashion, as Deep Blue Sea did with Dr. Susan McCallister.
Rules #4: Improvised Weapons
If you want to survive in a creature feature movie (or at least defeat the monster) you're going to need to pull a MacGuvyer. We're talking about Dutch's assortment of alien-traps in Predator, creative use of dynamite in Tremors and the willingness to use a cow, a lot of rope, and a helicopter to go fishing for alligators in Lake Placid.
Guns may take out a few of of the critters, but when push comes to shove, your real weapon is duct tape.
Corollary: No matter what environment you're in -- deep space, underwater research stations, remote jungles -- your single best weapon is fire. And like the saying goes, if fire isn't working, it's because you're not using enough of it. When fighting monsters from beyond imagining, a good solid flame unit is your best friend.