First, realize that, like automobile sticker fine print or long distance phone charges, when high dollars are involved many sellers will use deceptive tactics. Second, educate yourself (the web site for our diamond company contains excellent information). Third, deal exclusively with G.I.A. certified diamonds and become familiar with their grading. Fourth, keep the sale protected so you can return the diamond after third party review. Fifth, work with a competent appraiser, have him verify the diamond, buy a good quality loupe (its a lifetime investment) and don’t leave the appraiser until he shows you some landmarks on your diamond you can identify with your loupe.