Gold is a soft metal and thus can easily become scratched from everyday wear. Rings, especially gold wedding bands, seem to get scratched more easily than most jewelery and this can lead to a dull appearance. Gold bands luckily can be buffed to their previous condition rather inexpensively.
For at home fixes Jeweler's Rouge Polishing Clothes can be used to remove minor scratches in a gold wedding band. One side of the cloth is used to remove the scratches and create a smooth surface while the reverse side is used to polish the metal to a mirror finish. The clothes only cost about $5 and can be bought from most jewelers or jewelery supply stores.
For deeper scratches Jeweler's Rouge compound can be used. The compound, when spun onto the metal helps to remove deep scratches and polishes the metal to a mirror shine. The compound is used with a buffer's wheel and basically buffs out all the scratches in the metal by taking the ring down a layer.
A professional jeweler can buff a ring to it's original glory in about 24 hours. All you have to do is drop off the ring and pick it up the next day. Buffing of a gold ring can cost anywhere from $10-$30 depending on the jeweler you use. They will likely use Jeweler's Rouge to get a bright finish on the ring once again, but because they are professionals the finished product will look far better than buffing done at home.