a polishing cloth, unless the horn is REALLY dirty, then there is this stuff that you submerge the horn in, but this is only done for a complete overhaul.
I'd prefer to get a selmer silver polishing cloth. I used one on my old 1915 C.G.Conn C Melody Saxophone, and it turned out like a beauty. It used to be a musty brown and black combination. The cloths are around 10.95 when I bought mine this past summer.