Go to the cashier's cage at the casino where the chip was issued. Provide your ID and the chip itself. The cashier will verify the chip and exchange it for cash.

Whether they're poker chips or from other casino games, you can take chips home, or back up to your room if you're at a casino resort. Many players collect chips from various poker rooms, and there's nothing wrong with keeping a chip or two from a poker room if you're playing away from your local area.