A white button down paired with black pants/skirt is so easy to wear but you can get mistaken for the wait staff. An easy way to break this look up is accessories. A nice belt will give your waist definition and also make the look more interesting. Black is easy, why not try a red belt or even an animal print. Wearing a thick belt will give your waist much more definition and will become the point of interest for the outfit. A thin belt will be a nice add on. Play with the belts you own and see what works. The reason I recommended a red belt is because it looks great with black and white and it helps break up the outfit with some visual interest. Orange is a very popular colour this season, if you do not want to purchase any orange clothing try an orange belt. It will make your outfit current.
If all you have is a black belt wear it to define your waist and play with some necklaces or even a scarf. The scarf could add your pop of colour. I like to add black pearls with this outfit. Pearls are classic, black pearls are a bit more fun and not overdone by everyone.
Here are a couple of pictures of me wearing black, white and python. It was during Christmas of 2011 and I wanted to wear an outfit that was easy but still fashionable. The blouse and skirt are from Cassis, the belt is from BCBG and the necklace is from George. Would you ask me to take your order?