Men and women speak differently. Basically anywhere you go girls speak somewhat differently than guys. In Japan the differences between how a guy speaks and how a girl speaks is more noticeable. Not counting grammar and syntax, Japanese men generally speak in shortened huffs, while women tend to speak in artificially high octaves, elongating their word endings. Use of feminine words is called onna kotoba and feminine speech habits is called joseigo.
Some differences are:
Girls tend to refer to themselves in the third person more often than guys.
Sentence endings of wa, wa yo, wa ne, no ne, and no yo are feminine. kai, zo, ze, and yo are more masculine.
Women tend to use polite forms more frequently.
Women tend to omit the copula form da in favor of desu. For men, it is the other way around.
A lot of the humor of Ranma 1/2 is lost because in English the difference's between how a guy and a girl talk are much less pronounced. Ranma may call Akane a tomboy but she still talks like a girl. Ukyo, Ranma in girl-form, Shampoo, and Cologne talk like boys. For example, In the Manga Shampoo uses zo to end her sentences often. Ranma, Shampoo, Cologne, and Ukyo tend to use Omae as their preferred way of saying you which is masculine (though Ranma does also use significantly less polite versions as well i.e. insulting). When Ranma is pretending to be a real girl he uses Anta as you most of the time like Nabiki and Akane do. Though he (she at the time) also uses an even more polite form of you Anata like Kasumi and Kodachi do occasionally (btw Kodachi uses the politest most formal language in the manga). Tsubasa and Konatsu used feminine speech patterns. Since I'm already discussing speech patterns, I'd like to point out that Miss Hinako talks like a child even when in adult form.