Check for a hallmark stamp such as 10K, 14K, 18K, 22K, 24K, or 417, 585, 750, 916, 999
Look for discoloration or wear that reveals a different metal underneath
Use a magnet to see if the piece is strongly attracted
Rub the item on a ceramic plate and check for a gold-colored streak
Test with a gold testing acid kit
Weigh the piece and compare it to known gold items of similar size
Inspect for tarnish, since real gold does not tarnish easily
Check the clasp, edges, and hidden areas for signs of plating
Have a jeweler perform an X-ray fluorescence test
Have a professional appraise or authenticate the piece