Quality leather goods do require care. Most of the time, the oils from your skin will be enough to keep them in great shape, but I like to condition my bags once a year to make sure they last. It is also important to store them in a location where they can breathe, and with minimal humidity.
I recommend using a natural oil or beeswax conditioner. This is the product that I use on my bags and shoes. All Natural Leather Conditioner. This is also a great product to use if you are living in a rainy climate. If so, I recommend conditioning your leather products every 3-4 months.
Use a damp cloth for regular cleaning. If you get something on your bag, you can spot treat it with a natural dish soap and water or a saddle soap: saddle soap. When cleaning a bag, make sure you lightly dampen the whole panel of leather to avoid any water marks.
Be careful of using sunscreen or other chemical based products directly prior to using your leather goods, as it could stain the leather.