My wife has small fingers so a 1 carat diamond was huge so we went with a .67. I then looked for color and clarity. I tried to get a clarity that I could not see the any visable flaws with the naked eye. Also get flaws that are relatively clear. Do not get ones that are still carbon (black). Those show up to the naked eye much easier. Make sure the prongs are white gold or platinum because it makes a less color stone look like a better color stone. Yellow gold makes the stone look more yellow.