Wear a skirt: You can do it without flashing people. A-line or wider styles work best. Equip your bike with a skirt guard or fashion a garter out of a headband and safety pin. Skirt weights keep hems in check.
Wear heels: Pedaling in heels is easier than walking in them. Just make sure they fit properly.
Suit up: Invest in a pannier bag made to carry a suit without wrinkling it.
Stay dry: Invest in fenders if you commute year-round.
Safety first: Always wear a helmet (hopefully a stylish one), plus reflective tape and lights.
Don't sweat: Racing around like you're in the Tour de France will only make you perspire. Slow down and savor the views.