After the Diamond is Located
After you believe you have located the right stone for the customer, call them to give them the details. This will be a good indicator to see if they are still on the same page with you. If they shy away at least the diamond was not shipped unnecessarily. Chances are though, they will still be interested if you've come this far with them. Give them all the details of the diamond including the negative ones if there are any. If they are interested in viewing it, it is preferable to set up an appointment to show the diamond before you order it.