recovery_boot_asus_I:hold <kbd>Volume Up</kbd> + <kbd>Power</kbd>. Keep holding both buttons until the words "Fastboot Mode" appear on the screen, then release. Now with the volume rocker select "Recovery mode", then press <kbd>Power</kbd>.
recovery_boot_lg:hold <kbd>Volume Down</kbd> + <kbd>Power</kbd>. When the LG logo appears, release both buttons and then hold them again. Then answer YES to erase all user data & restore default settings (If you have TWRP installed it will not delete anything).
recovery_boot_lg2:hold <kbd>Volume Down</kbd> + <kbd>Power</kbd> until the LG logo appears, then release <kbd>Power</kbd> for a second and hold it again until the recovery comes up.
recovery_boot_lg3:and usb unplugged, hold <kbd>Volume Down</kbd> + <kbd>Power</kbd>. When the LG logo appears, release both buttons and hold <kbd>Volume Up</kbd> + <kbd>Volume Down</kbd>.
recovery_boot_victara:hold <kbd>Volume Down</kbd> + <kbd>Power</kbd>. On the next screen use <kbd>Volume Down</kbd> to scroll to Recovery and then press <kbd>Volume Up</kbd> to select.
recovery_boot_bullhead:hold <kbd>Volume Down</kbd> + <kbd>Power</kbd>. On the next screen choose Recovery Mode.
recovery_boot_bixby:hold <kbd>Volume Up</kbd> + <kbd>Bixby</kbd> + <kbd>Power</kbd>. When the blue text appears, release the buttons.