An authentic Louis Vuitton bag is an investment. The expensive handbags should never be allowed to get wet, and the owner should never use it carelessly. Should the bag get dirty, it can not be cleaned with regular soap and water.
The Monogram and Damier Collection bags are made from a coated canvas and trimmed with leather. The coated canvas (usually the body of the bag) is somewhat water resistant, but not waterproof. Use a clean and dry cloth to clean the surface.
If the bag is made of vachetta leather, carry it on your arm or shoulder, not in your hands. Your hands could pass microscopic dirt and oils to the leather that will be hard to get out.
Wipe the bag every now and down with a baby wipe. This may slightly darken the leather, but the color will be even all over the bag. Never use chemicals on the bag. If the leather becomes dry (from not carrying it at all) it can crack. Use a leather lotion to counter any signs of cracks.
When the bag is not in use, store it in the felt pouch that came with the bag.