Press Volume Down + Power untill you see a white text on the screen then release the buttons and press Volume UP (you have 5 seconds to do it)
Note: This works for both Stock and Custom recovery.
Cold Boot - FastBoot - Wipe Data Menu **
Press Volume Down + Power untill you see a white text on the screen then release the buttons.Use Volume Down to navigate and Volume Up to confirm your selection.You have 10 seconds to make your choise,or else the system will do a Cold Boot by default.
Note: FastBoot mode is available only if you unlocked the bootloader.
** Boot to APX mode **
Press Volume Up + Power for 5 seconds,the device will vibrate and your screen will be OFF.
Note: APX mode is needed if you want to use NVflash.
Note 2: Press Power button for 10 seconds to exit APX mode
Credit to this unusually helpful thread