Buy from someone you trust. You are not going to be able to determine the difference between two similar appearing stones.
Diamond certificates don’t tell the whole story. Stick to certificates performed by the American Gem Society (AGS), Gemological Institute of America (GIA) and ask lots of questions.
Examine diamonds unmounted, using a gem microscope with dark field illumination. Don’t bother with a loop.
Look at the proportions on the stone. A well cut diamond should fit within these parameters.
Determine a budget and stick to it. Spend most of your money for the center stone. You can always remount the gemstone in another ring.
Set diamonds D to I in color in white gold. Set diamonds J to Z in yellow gold.
Set the diamond as low as possible. It may be prettier set higher but at this extended height you are more likely to hit the mounting and dislodge the stone.
Keep in mind if you buy a diamond with a 30, 60, 90 day no payment period or pay the diamond off over time someone is paying the interest charges. That someone is you.
Be sure to ask if the diamond has been laser drilled or clarity enhanced. A friend of mine once commented, “You may not always get what you think you are paying for but you can be assured if you don’t pay for it you’ll never get it!”
Deals that are too good to be true are just that!