Protip: If you wanna sell your gold necklace or earrings or whatever wait until about Christmas time. That is when the gold price is usually the highest all year, because the demand for gold jewelery and the like is the highest at that time. Look for the karat engraving: If it is 100k, the gold is 100 fine gold, which is not common in jewelery, because pure gold is too soft to make outlasting pieces with it.
My grandpa recently gave me a golden wristband, weighing 100 g. The fine gold percentage is 750, meaning there is 75g of pure gold used. He told me he bought it for about 200 DeutschMark 7 years ago. Now it's worth more than 2000 Dollars. Right now the gold price is at about 1135,90 USD per fine ounce. It went down before easter, but has risen again due to the holiday.
If you wanna sell your gold, don't use those bullshit websites or TV deals. Go to a gold dealer(jewelery in your town, preferably to more than one, and compare prices. Those people are just looking to rip off your ignorant ass, too, but the deal will be way better.