Frequent operation errors are another sign that a skimmer may be in use. Skimmers often affect the magnetic strip and can slow down the function of the terminal.
Is there a stylus attached? Terminals with skimmers don’t allow the stylus to be attached.
Pay close attention to the terminal you are using as all regular terminals will have a stylus attached in order for a signature to be made.
Even with these tips, it can be difficult to decipher a real terminal from a skimmer. Another good tip is to keep a separate debit card on hand that only holds a certain amount of funds.