Check for hallmarks or stamps such as 10K, 14K, 18K, 22K, 24K, or 417, 585, 750, 916, 999
Use a magnet to see if the item is attracted
Test the weight against expected size and density
Look for discoloration, fading, or worn areas revealing a different metal underneath
Rub the item on a testing stone and apply acid test solutions
Use a gold testing kit
Perform a ceramic scratch test on an unglazed tile
Check for a strong color change with nitric acid
Use an electronic gold tester
Compare the item with known genuine gold pieces
Have a jeweler or assay office test it professionally