There are several ways to tell if gold is real. As mentioned above, any genuine gold pieces will be stamped with a hallmark stating the content of pure gold that it contains. Always check for the hallmark. The stamp is usually found on the clasp of a necklace or bracelet, or on the inner band of a ring.
A few hallmarks, such as EPNS, EPBM, and GF, also indicate that a piece is not real gold. As with Gold Electroplate, these symbols indicate that a piece is not actually made of gold but another metal, and has simply been gold plated.
A simple test is one that can be performed at home to check if gold is real. Gold is a heavy metal, and therefore, real gold should sink. Drop your gold item into a jug of water. Any piece of supposed gold jewelry that floats is likely to be fake gold.