Tools of Characterization
Characterization in Star Trek II: The Wrath of Khan
Clothing
This isn't a movie to be coy about who the good guys and bad guys are. The famous red, blue and yellow uniforms in the original show are nowhere to be seen here. Instead, Starfleet's officers wear a more dignified wine-colored uniform, which is more in keeping with classic military designs.
(Fun note: the original uniforms from the TV show were designed to take advantage of color TV, which was a Big Deal in the 60s. People had become much more blasé by 1982, which is why Wrath of Khan redesigned the whole look to reflect something a little less pop art.)
In any case, we know who the good guys are: they're the ones in red. The villains, on the other hand, are much scruffier, wearing the remnants of Starfleet outfits, yes (you can see that funky symbol around Khan's neck and elsewhere on their costumes), but torn, beaten up, and generally looking like they spent the last fifteen years living under a sand dune. (Which they pretty much did.)
It's the perfect look for a scurvy band of space pirates, as well as telling us at a glance who's wearing the white hats and who's wearing the black ones.
Oh yeah—and check out that mullet on Khan. If that doesn't scream evil, we don't know what does.
Actions
Kirk and the Enterprise work to help the scientists on Regula One, and by extension the galaxy. Khan and his crew blow things up a lot. Kirk and the heroes resolutely refuse to dump space eels into anyone's ears.
Khan? Not so much. And while Khan is happy to sacrifice himself if it means killing his enemies, Spock cheerfully repeats the feat in order to save everyone. That's a pretty smooth way to delineate the good guys from the bad.
Speech and Dialogue
Kirk speaks in terms of tactics and strategies.
McCoy is fiery and emotional.
Spock is a passionless pool of calm.
And Khan? Well, Khan has that special kind of nutty in his tone that speaks to an emotional volcano ready to go Mount St. Helens on everyone.
We see a lot about who these characters are not just in what they say, but in the emotional tone they use to say it. It's partially informed by the original series, which had plenty of time to establish these verbal tics. But by evoking it here, Star Trek II can connect us to the characters we've come to love simply by letting them plot, rage, and logically dissect the proceedings the way they always have.
Social Status
The crew of the Enterprise is strictly regimented, with different ranks delineating who gets to yell "frog" and who gets to jump.
On a subtler level, young members of the crew like Saavik are definitely junior grade compared to the old farts like Kirk and Spock (and to a certain extent Carol Marcus).
Contrast that with Khan, whose crew features a much more free-form social status, basically defined as Everyone Does What Khan Says. In either case, you can tell a lot about who these people are by who they answer to and how they answer to him (or her).