Hmm.
Sanding and polishing are two ways to go about doing it.
For your frets I'd suggest a fine-grit sandpaper (grade 1000), followed by metal polish (brasso).
Pickup screws and tremoloes are a trickier issue, but a rougher sand-paper to remove the rust would be a wise move, followed by a cleaning with naptha (lighter fluid) and a once-over with metal polish.
After you're done with that 3-step with the screws and tremolo I'd suggest you get a can of clear lacquer and give the screws and tremolo (I'm thinking you're talking about the saddles or the tremolo body individually right?) a thin coat of lacquer for individual parts.
Remember: lacquer for individual parts ONLY. Lacquer helps prohibit the growth of rust due to the isolation of the metal parts from moisture.