How to handle customer complain the policy"No Return, No exchange"for the product like clothes and shoes that has been used,but the customer denied?

Its very simple dear,before selling the product to the customer clearly inform them that no return no exchange once the product sold out tell in the way so that he cannot come back,but if in case manufacture defect which may he dint observe at the time purchase so make sure that he will check everything before he buys.