Final answer:
When a credit card is declined, the server or cashier should discreetly inform the guest and politely suggest an alternative payment method, while ensuring there are no technical issues with the transaction.
Step-by-step explanation:
When a guest's credit card has been declined, the server or cashier should handle the situation discreetly and professionally. They should inform the guest quietly that the card has been declined and suggest that they try another form of payment or another card. It is important to remain calm and courteous, avoiding any actions that could embarrass the guest. Additionally, the server or cashier should check to make sure that the credit card machine is working properly and that the card was swiped correctly to avoid any technical errors that might have caused the decline.