For deliverable contracts such as cl and gc, first notice day comes before the last trading day. Most brokers force retail traders to close or roll a day or two ahead, or they liquidate the position for you.
Cash-settled index futures have no delivery and no first notice day.
Example: crude's first notice is typically a few days before the 25th of the month before delivery. A trader long the front month must roll by then or be closed out at the broker's discretion.
Related: settlement, roll, contract-month, cl