Brass hardware may require a little maintenance from time to time as it naturally tarnishes. 

Brass, like silver, tarnishes because its metal components—copper and zinc—are exposed to oxygen. This is a natural process. The oils in your skin also have an effect on brass, so the more an item is used, the more corrosion or tarnish can occur. Water can also contribute to aging your brass, so you want to make sure you aren’t submerging them into too much water.

If you spill anything acidic on your hardware and don't clean it immediately it will etch through the surface coating and leave a bright mark. You should attend to problems as they arise with warm water, a PH neutral soap can be applied if required.

Do not use any scouring or abrasive pads / cloths to clean your hardware, they will mark the surface. 

Do not use any household bleach or cleaning products on the hardware. Brass is naturally self cleaning in terms of bacteria resistance and this was the main reason for use in hospitals in the Victorian era (lots of interesting info can be found online.)