I've been taking care of gold-plated guitar gear for years -- what I'm using is a good grade of carnauba wax on all metal parts within hours of unpacking the sucker (you can use this on the finish as well; this stuff is, after all, car paint). This helps protect it from acids and scratching. The gold is very thin plating (as mentioned elsewhere) and the main way that it's damaged is that it's simply rubbed off. The second way it's damaged is that the base metal beneath it corrodes and allows the gold to flake off (very small flakes). Waxing helps protect it in both cases. Do NOT use metal polishes; you'll just accelerate the process of wearing off the gold. Re-Wax your guitar as often as you'd wax a new car.
