In order to preserve your brass furniture and keep it as good as new, you need to clean it by washing it with detergents and a solution of one tablespoon of salt and two tablespoons of vinegar. A pint of water, if added, will prove to be better. If you wish to clean off the dirt by the sides, then you may use a solution of ammonia on a toothbrush. If the brass is corroded badly, then immerse it in a solution of washing soda, and wipe it repeatedly.
You can obtain a glass brush from a jeweler in order to brush off the stained parts. If you see spots of corrosion, then rub them off with scouring powder and a piece of cloth. If you completely fail to prevent the scratches, then polish it with a paste of finely ground chalk which you can obtain from a DIY shop. Brass handles, if possible, should be removed before cleaning; otherwise the polish can damage the wood.