John, our narrator de jure, interviews a lot of people about past events, so a lot of characterization is handed down through direct characterization. That is, John or another character just flat out tells us what someone is like. Newt tells John that his father "just wasn't interested in people" (6.4). We're also given direct characterization about Earl McCabe as others inform us how he had to play the villain to Bokonon's saint and how this life wore him down to suicide.
It happens less often with characters John meets in the present, but, even then, direct characterization pops up from time to time. For example, John mentions he has never "seen a human being better adjusted to such a humiliating physical handicap" as Newt, giving us a pretty good idea of the character we only previously knew in letters (59.5).
Names can be an indicator of characterization, but tread warily here. Cat's Cradle is a satire, so many of the names are supposed to be jokes. For example, Naomi Faust is named after the character of Germanic legend who gave his soul to the devil for knowledge and truth. But Naomi doesn't "[understand] how truth, all by itself, could be enough for a person" (25.8).
Sure, as a joke, it's a tad literary and dry, but it's still technically a joke.
Other characters present similar name-jokes. Mona is the sexy poster girl of San Lorenzo, and the name "Mona" suggests a sexy moan. But she remains completely uninterested in sex, and John believes she "[has] no idea what lovemaking [is] all about" (118.19). And speaking of John: he assumes the name of the Biblical prophet, but whereas John in the Bible was said to bring the truth from God, our John admits to bringing lies and only lies.
You don't really want to be a scientist in Cat's Cradle. Both Felix Hoenikker and Asa Breed feel their work is separate from human affairs. Now, this characterization doesn't make either character evil or villainous, but it does suggest that they're not really willing to accept reality.
Writers, on the other hand, get a little more love. John mentions that when "a man becomes a writer, I think he takes on a sacred obligation to produce beauty and enlightenment and comfort at top speed" (103.13). Julian Castle agrees, believing a deprivation of literature would cause a man to die either of "putrescence of the heart or atrophy of the nervous system" (103.18).
So, scientists are characterized as truth seekers who need to reconsider the morality of their truth. On the other hand, writers need to keep on writing so beauty can continue to exist in the world.