Two women may kiss and hug, caress each other's bodies for hours, or have quick sex. One person, both, or neither may orgasm once or several times. As you see, much of this is similar to heterosexual sex. Often, there is an incorrect expectation that a woman would know how to be a perfect lover to another woman, since she knows what pleases her. However, all women are different.
Communication is key, as in all types of sexual relationships.
Remember that having sex with a woman for the first time, or at any time, involves a lot more than what happens just sexually. There's also a great women's bookstore downtown that has a good assortment of lesbian materials.