It depends on how dirty it is. Signet used to sell tools specifically designed to clean male and female rca connections. Available from mail order houses like musicdirect or elusive disc. Very fine sand paper can work. You can also use flux for soldering or solvents used to clean pipes before soldering. A litle still wool can get those stubborn deposits off. Obviously you want to be extremely careful not to mar the finish.
When applying contact enhancers remember less is more.
When applying contact enhancers remember less is more.