Roses - for the Eternal Romantic, or, the classy chick with a cliched sense of what's acceptable, depending on your point of view. Once you get past red roses, remember that crimson is a better choice.
Gerber Daisies - for the Sweet Young Thing, the pretty girl with the stars in her eyes and innocence in her heart. Alternatively, these would make a lovely 80th birthday boquet for your childless great-aunt Lila.
Carnations - For the Offbeat Boheme, the edgy beauty with the fiery soul. Someone who doesn't give a damn about what flowers mean, because the damned things just look so pretty.
Lillies - for the Temperamental Diva - a profusion of these flaming, exotically beautiful blooms is sure to ease your way to her heart. Take care not to give her funereal white, though, or they might end up gracing your coffin-side, prima donna that she is.
Orchids - for the Woman of your Dreams - delicate and ethereally exquisite, yet evocative of a lush tropical earthiness. It doesn't matter what colour they are, because orchids never go out of style and they're very easy on the eye. Too bad I can't say the same about your wallet.
Tulips - for the Wholesome Beauty, with a hidden quirky side. Nothing will charm her more than these blushing blossoms. Unless of course, she prefers vintage pendants from the 1920's - I told you, she's quirky.