iPhone 8 or later, including iPhone SE (2nd generation): Press and quickly release the volume up button. Press and quickly release the volume down button. Then, press and hold the side button until you see the recovery-mode screen.
iPhone 7, iPhone 7 Plus, and iPod touch (7th generation): Press and hold the top (or side) and volume down buttons at the same time. Keep holding them until you see the recovery-mode screen.