Give the waitress your debit card when she gives you the check. If you must pay at the cash register, then take your check to the register and hand the cashier your check and debit card.
Find the "Merchant Copy" of the receipt. The waitress or cashier will give you two receipts back with your debit card; one is a merchant copy that the store keeps, and one is a customer copy that you keep. The merchant copy is usually on top of the customer copy.
Write down the gratuity amount on the line next to "Tip Amount" or "Gratuity Amount." Circle the amount. Write down the total, with the gratuity included. For example, if your total before the tip was $25.00 and you included a $5.00 tip, then your total would be $30.00. Circle the total amount and sign your name on the "Signature" line.
Leave the receipt on the table, or hand it to the cashier if you are paying at the register. The waitress can then collect your tip from the register.