Just ask LOTS OF questions and bring a loupe when you buy diamonds and don't buy if you don't get a full refund of your money with that guarantee of a refund in writing... (NOT store credit)
ugh I hate stores that don't give a refund! I bought a WG amethyst ring from a local store probably about 7 years ago and it turned out to be 10k not 18k and a mystic topaz!!! I took it back and they told me they do not offer refunds. I spoke with the owner and showed him my receipt stating 18k WG and an amethyst for the center stone....they grudgingly gave me a refund after about an hour of arguing. I learned my lesson after this experience!